We've had a minor wrinkle with the latest pre-release version of Forefront 2010: after an SP2 upgrade Forefront continues to do its job but Exchange config settings (sender filter lists etc) can't be updated. It complains that not all Forefront services are running )they are and to check that powershell is installed (it is).
To be expected with pre-release products - I will check to see if a Forefront repair makes any difference and report back.
EDIT: A reinstall didn't work. I'd expect an updated build shortly - obviously the Exchange Management Console changes in SP2 have created a slight incompatibility with the Forefront Console but you can workaround this by working in the Exchange console directly.