Having had the application running successfully at the pure package for several weeks, a Click Once update failed.

The error message “requires assembly CrystalDecisions.ReportAppServer.ReportDefModel Version 12.0.0.11.0.0 be installed in the Global Assembly Cache”

When I checked back to an old working installation, I found the Crystal Reports references to be a later version (13)

SOLUTION

I removed all references to Crystal Decisions from my project, then browse to add in the new references:

Path on my pc Shown Below

C:\Program Files (x86)\SAP BusinessObjects\Crystal Reports for .NET Framework 4.0\Common\SAP BusinessObjects Enterprise XI 4.0\win32_x86\dotnet