In order for us to understand the whole issue and assist you in the best possible way, could you provide some more information about your scenario?
1) What technology you are using: WPF, Silverlight, ASP, WinForms?
2) Do you change the version of the .NET when converting the solution?
3) Which assemblies of Telerik OpenAccess ORM you are using and what is their versions?
4) Do you load Telerik OpenAccess ORM assemblies at runtime?
The issue may have appeared when you were converting the solution and if some versions of the assemblies used were changed. You could try to remove all of Telerik OpenAccess ORM assemblies and add them again, when you should make sure their versions are the same.
We are looking forward for your feedback.
the Telerik team
Free Webinar: OpenAccess Integration in Sitefinity. SIGN UP NOW.