I was recently on a customer site and had configured the Synchronization Service including creating Management Agents, projections, joins etc. I then realised i had not installed update 2 for FIM, so i proceeded to download and install the update through windows update only to be met with the following error:

Error 25070.Error connecting to database FIMSynchronizationService. Invalid class string

Doh! Silly me, with the databases homed on a remote SQL server the SQL Native Client must be installed on the FIM server. I had forgotten to do this, after doing so the update completed without issue