Unable to save and publish publishing pages in document library

Hi,

As per the business requirement i am creating a publishing page with a custom page layout in a document library,

Document library's primary content type is same as the custom page layout's content type.

After creating the page and providing the input in the fields that are part of page layout, while trying to save and publish the page i am getting  the follwing error when searched in logs

System.ArgumentException: Invalid SPListItem. The SPListItem provided is not compatible with a Publishing Page.    at Microsoft.SharePoint.Publishing.PublishingPage.GetPublishingPage(SPListItem sourceListItem)     at Microsoft.SharePoint.Publishing.Internal.WebControls.PublishingPageStateControl.RaisePostBackEventForPageRouting(String eventArgument, SPRibbonCommandHandler control, RaisePostBackEventDelegate raisePostBackEventDelegate)     at Microsoft.SharePoint.Publishing.Internal.WebControls.PublishingPageSaveAndStopEditHandler.RaisePostBackEvent(String eventArgument)     at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)     at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

note: This was not working post upgrade from SP 2007 to 2010, and it was working as expected in the SP 2007 version

Any help on this would be appreciated.