COMException (0x80004005): Cannot complete this action. Please try again.

The other day I received a long but still not too meaningful exception when opening a SharePoint site:

Server Error in ‘/’ Application.

Cannot complete this action.

Please try again.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Runtime.InteropServices.COMException: Cannot complete this action.

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Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[COMException (0x80004005): Cannot complete this action.

Please try again.]
Microsoft.SharePoint.Library.SPRequestInternalClass.GetFileAndMetaInfo(String bstrUrl, Byte bPageView, Byte bPageMode, Byte bGetBuildDependencySet, String bstrCurrentFolderUrl, Boolean& pbCanCustomizePages, Boolean& pbCanPersonalizeWebParts, Boolean& pbCanAddDeleteWebParts, Boolean& pbGhostedDocument, Boolean& pbDefaultToPersonal, String& pbstrSiteRoot, Guid& pgSiteId, UInt32& pdwVersion, String& pbstrTimeLastModified, String& pbstrContent, Byte& pVerGhostedSetupPath, UInt32& pdwPartCount, Object& pvarMetaData, Object& pvarMultipleMeetingDoclibRootFolders, String& pbstrRedirectUrl, Boolean& pbObjectIsList, Guid& pgListId, UInt32& pdwItemId, Int64& pllListFlags, Boolean& pbAccessDenied, Guid& pgDocId, Byte& piLevel, UInt64& ppermMask, Object& pvarBuildDependencySet, UInt32& pdwNumBuildDependencies, Object& pvarBuildDependencies, String& pbstrFolderUrl, String& pbstrContentTypeOrder) +0
Microsoft.SharePoint.Library.SPRequest.GetFileAndMetaInfo(String bstrUrl, Byte bPageView, Byte bPageMode, Byte bGetBuildDependencySet, String bstrCurrentFolderUrl, Boolean& pbCanCustomizePages, Boolean& pbCanPersonalizeWebParts, Boolean& pbCanAddDeleteWebParts, Boolean& pbGhostedDocument, Boolean& pbDefaultToPersonal, String& pbstrSiteRoot, Guid& pgSiteId, UInt32& pdwVersion, String& pbstrTimeLastModified, String& pbstrContent, Byte& pVerGhostedSetupPath, UInt32& pdwPartCount, Object& pvarMetaData, Object& pvarMultipleMeetingDoclibRootFolders, String& pbstrRedirectUrl, Boolean& pbObjectIsList, Guid& pgListId, UInt32& pdwItemId, Int64& pllListFlags, Boolean& pbAccessDenied, Guid& pgDocId, Byte& piLevel, UInt64& ppermMask, Object& pvarBuildDependencySet, UInt32& pdwNumBuildDependencies, Object& pvarBuildDependencies, String& pbstrFolderUrl, String& pbstrContentTypeOrder) +625

[SPException: Cannot complete this action.

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Microsoft.SharePoint.Library.SPRequest.GetFileAndMetaInfo(String bstrUrl, Byte bPageView, Byte bPageMode, Byte bGetBuildDependencySet, String bstrCurrentFolderUrl, Boolean& pbCanCustomizePages, Boolean& pbCanPersonalizeWebParts, Boolean& pbCanAddDeleteWebParts, Boolean& pbGhostedDocument, Boolean& pbDefaultToPersonal, String& pbstrSiteRoot, Guid& pgSiteId, UInt32& pdwVersion, String& pbstrTimeLastModified, String& pbstrContent, Byte& pVerGhostedSetupPath, UInt32& pdwPartCount, Object& pvarMetaData, Object& pvarMultipleMeetingDoclibRootFolders, String& pbstrRedirectUrl, Boolean& pbObjectIsList, Guid& pgListId, UInt32& pdwItemId, Int64& pllListFlags, Boolean& pbAccessDenied, Guid& pgDocId, Byte& piLevel, UInt64& ppermMask, Object& pvarBuildDependencySet, UInt32& pdwNumBuildDependencies, Object& pvarBuildDependencies, String& pbstrFolderUrl, String& pbstrContentTypeOrder) +748
Microsoft.SharePoint.SPWeb.GetWebPartPageContent(Uri pageUrl, PageView requestedView, HttpContext context, Boolean forRender, Boolean includeHidden, Boolean mainFileRequest, Boolean fetchDependencyInformation, Boolean& ghostedPage, Byte& verGhostedPage, String& siteRoot, Guid& siteId, Int64& bytes, Guid& docId, UInt32& docVersion, String& timeLastModified, Byte& level, Object& buildDependencySetData, UInt32& dependencyCount, Object& buildDependencies, SPWebPartCollectionInitialState& initialState, Object& oMultipleMeetingDoclibRootFolders, String& redirectUrl, Boolean& ObjectIsList, Guid& listId) +2578
Microsoft.SharePoint.ApplicationRuntime.SPRequestModuleData.FetchWebPartPageInformationForInit(HttpContext context, SPWeb spweb, Boolean mainFileRequest, String path, Boolean impersonate, Boolean& fGhostedPage, Byte& verGhostedPage, Guid& docId, UInt32& docVersion, String& timeLastModified, SPFileLevel& spLevel, String& masterPageUrl, String& customMasterPageUrl, String& webUrl, String& siteUrl, Guid& siteId, Object& buildDependencySetData, SPWebPartCollectionInitialState& initialState, String& siteRoot, String& redirectUrl, Object& oMultipleMeetingDoclibRootFolders, Boolean& objectIsList, Guid& listId, Int64& bytes) +2081
Microsoft.SharePoint.ApplicationRuntime.SPRequestModuleData.GetFileForRequest(HttpContext context, SPWeb web, Boolean exclusion, String virtualPath) +727
Microsoft.SharePoint.ApplicationRuntime.SPRequestModule.InitContextWeb(HttpContext context, SPWeb web) +164
Microsoft.SharePoint.WebControls.SPControl.SPWebEnsureSPControl(HttpContext context) +665
Microsoft.SharePoint.WebControls.SPControl.GetContextWeb(HttpContext context) +41
Microsoft.SharePoint.WebControls.SPControl.GetContextSite(HttpContext context) +49
Microsoft.SharePoint.ApplicationRuntime.SPRequestModuleData.GetSiteForRequestFile() +51
Microsoft.SharePoint.ApplicationRuntime.SPRequestModuleData.FetchWebPartPageInformationForInit(HttpContext context, SPWeb spweb, Boolean mainFileRequest, String path, Boolean impersonate, Boolean& fGhostedPage, Byte& verGhostedPage, Guid& docId, UInt32& docVersion, String& timeLastModified, SPFileLevel& spLevel, String& masterPageUrl, String& customMasterPageUrl, String& webUrl, String& siteUrl, Guid& siteId, Object& buildDependencySetData, SPWebPartCollectionInitialState& initialState, String& siteRoot, String& redirectUrl, Object& oMultipleMeetingDoclibRootFolders, Boolean& objectIsList, Guid& listId, Int64& bytes) +1824
Microsoft.SharePoint.ApplicationRuntime.SPRequestModuleData.FetchWebPartPageInformation(HttpContext context, String path, Boolean impersonate, Boolean& fGhostedPage, Byte& verGhostedPage, Guid& docId, UInt32& docVersion, String& timeLastModified, SPFileLevel& level, String& masterpageUrl, String& customMasterPageUrl, String& webUrl, String& siteUrl, Guid& siteId, Object& buildDependencySetData) +475
Microsoft.SharePoint.ApplicationRuntime.SPRequestModuleData.GetWebPartPageData(HttpContext context, String path, Boolean throwIfFileNotFound) +1559
Microsoft.SharePoint.ApplicationRuntime.SPVirtualFile.GetFile(String virtualPath, Boolean fetchContent) +148
Microsoft.SharePoint.ApplicationRuntime.SPVirtualFile.GetFile(String virtualPath) +43
Microsoft.SharePoint.ApplicationRuntime.SPVirtualPathProvider.GetFile(String virtualPath) +290
System.Web.Hosting.VirtualPathProvider.GetFileWithCheck(String virtualPath) +31
System.Web.FormatterWithFileInfo.GetSourceFileLines(String fileName, Encoding encoding, String sourceCode, Int32 lineNumber) +205
System.Web.DynamicCompileErrorFormatter.get_MiscSectionContent() +766
System.Web.ErrorFormatter.GetHtmlErrorMessage(Boolean dontShowSensitiveInfo) +998
System.Web.HttpResponse.WriteErrorMessage(Exception e, Boolean dontShowSensitiveErrors) +11056428
System.Web.HttpRuntime.FinishRequest(HttpWorkerRequest wr, HttpContext context, Exception e) +461

Version Information: Microsoft .NET Framework Version:2.0.50727.4927; ASP.NET Version:2.0.50727.4927

I had no clue from the exception and the callstack about what could go wrong but I was lucky that I knew what were my last changes in the code so I just started to review and rollback them.

The error itself was quite evident, too bad it only resulted in that runtime exception.
We use a master page file which has a codebehind class also. A property however that is used in the master page as an inline code (<% =MyProperty %>) was declared private static in the codebehind (copy-paste error).
After changing the declaration to public the exception was gone.

Probably many issues may result in that exception but evidently this is one of them.