Had this error on a client machine today i was running migration scripts on with Scribe, it seemed to create this error in the trace log everytime we tried to connect.
The workaround was to obtain the microsoft.xrm.client.dllfrom the SDK and copy it into the
DRIVE\Program Files\Microsoft Dynamics CRM\Server\Bin folder.
After a IISRESET, the Scibe connection adapter started to connect to the CRM Services.
Thanks
Jonathan