Hi Moshe;
I would try ....
1) stepping through the code via the Debugger. Maybe you can see an issue just before your Create fails.
2) wrap your current code in a TRY..CATCH and see if the exception object gives you any more useful information.
3) Try regenerating all your proxies.
Note: if your running the IDE under W2008R2 - PB is not certified for any server development.
Regards ... Chris