Here are 2 common problems that I see in the field and I know people spend a lot of frustrating time trying to track them down.
Error: Attempted to read or write to protected memory
This is actually a .Net framework 2.0 error
Error:DCOM Search errors in the event log
Fix: Configure DCOM. This KB describes the process
But you will have to search for the GUID (as listed in the event log error) in the registry to find the process in dcomcnfg.exe. It may also be a different account (rather than NT AUTHORITY NETWORK SERVICE) that you need to grant launch and activation permissions on.