Getting HTTP 403/500 errors when accessing SharePoint 2010 pages

Hi,

I'm getting intermittent HTTP 403/500 errors when accessing SharePoint Foundation 2010 pages.

When it happens, any SharePoint pages I access I get a HTTP 403 error (example: /sites/test/default.aspx) . If I don't specify a page, I get a HTTP 500 error (example: /sites/test/). What's odd is that I have non-SharePoint .NET applications running on the same server under the "_layouts" directory and those still work just fine.

After recycling the IIS application pool, it starts to work again, but sometime won't stay up very long.

Does anyone encounter this problem before?

TIA

Also, I'm hoping to understand what the "Microsoft.SharePoint.Library.SPRequest.GetFileAndMetaInfo" method does to help me track down this issue. If you have any info on what the above method is doing, I really appreciated.

EVENT LOG

Nothing

ULS LOG

System.Runtime.InteropServices.COMException: Cannot complete this action.  Please try again.   
 at Microsoft.SharePoint.Library.SPRequestInternalClass.GetFileAndMetaInfo(String bstrUrl, Byte bPageView, Byte bPageMode, Byte bGetBuildDependencySet, String bstrCurrentFolderUrl, Int32 iRequestVersion, Boolean& pbCanCustomizePages, Boolean& pbCanPersonalizeWebParts, Boolean& pbCanAddDeleteWebParts, Boolean& pbGhostedDocument, Boolean& pbDefaultToPersonal, Boolean& pbIsWebWelcomePage, 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)   
 at Microsoft.SharePoint.Library.SPRequest.GetFileAndMetaInfo(String bstrUrl, Byte bPageView, Byte bPageMode, Byte bGetBuildDependencySet, String bstrCurrentFolderUrl, Int32 iRequestVersion, Boolean& pbCanCustomizePages, Boolean& pbCanPersonalizeWebParts, Boolean& pbCanAddDeleteWebParts, Boolean& pbGhostedDocument, Boolean& pbDefaultToPersonal, Boolean& pbIsWebWelcomePage, 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)