Business Portal 5.1 SP3 - You receive a "Server was unable to process request" error message when you try to modify a BP user record

Hello,

Whenever I modify a user permission I'm getting an error. Navigation: Site Actions/ Site Settings/ Business Portal Administration/ Users/ Permissions Tab

I stumbled on KB906719, but it applies to Microsoft Business Solutions Business Portal 2.5 Feature Pack. Does anyone one of an updated solution or workaround for BP 5.1? Any taker?

Thanks in Advance