This is such a major and ridiculous bug on Microsoft's part:
Windows Server 2008 SP2
Network Protection Services is implemented
User Profile service stops periodically, preventing users from authenticating. A message beginning with "Faulting application svchost.exe_IAS, version 6.0.6001.18000" is recorded in the event log.
A user enters a valid username, but the password is incorrect. At this point the service crashes.
So far there is none. You either have to roll back to a previous service pack or not use PEAP. Look for a hotfix or expect this to be a fix in SP3.