BizTalk 2009 Orchestration Fails to Find References on External Assemblies
If you’re developing BizTalk 2009 solutions (Orchestrations) and you’ve split your schemas out into alternative assemblies (projects) – sometimes you’ll get odd not found issues with some (if not all) of the types in those referenced assemblies. You can try everything – recompile, de-gac, re-gac, – doesn’t matter.
Well there’s a hotfix for this:
http://support.microsoft.com/kb/977428/en-us
FIX: You experience various problems when you develop a BizTalk project that references another BizTalk project in Visual Studio on a computer that is running BizTalk Server 2009