The OutputPath property is not set Follow

This is driving me to the point of tears (metaphorically speaking lol)..

I'm using msbuild to build and deploy some web applications (.net 3.5+). What is odd is that i'm getting this error on shared projects but not in all solutions that use them. For example solution A includes shared project PaymentProviders.csproj and will build fine. However solution B includes the same shared project and i get an error...

"Error]  C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets(483,  9): The OutputPath property is not set for project  'PaymentProviders.csproj'.  Please check to make sure that you have  specified a valid combination of Configuration and Platform for this  project.  Configuration='Prelive'  Platform='AnyCPU'.  You may be seeing  this message because you are trying to build a project without a  solution file, and have specified a non-default Configuration or  Platform that doesn't exist for this project."

Any ideas are appreciated.

Regards
Sean