Symptom: After updating NVC to NEM the Exchange IS is not starting
Problem:The NVC had a flag set if the NVC was on the same server as Exchange. If this flag is set and NVC is no longer available, Exchange cannot start the informationstore.
SolutionTo fix this issue, go to the registry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\VirusScan

Change the value from 1 to the following:

Key: Enabled
Type: REG_DWORD
Value: 0