Incase anyone else has a **** load of NT4 boxes and you decide to throw SAV9 on them, prepare for the madness of OleMainThreadWndName errors. To spare someone the surprise of this, take a peak at this tech bulleton:

Symantec AntiVirus Corporate Edition, Release MR2
Fix ID: 1-2XZVIR
Shutdown error on Windows NT 4: "OleMainThreadWndName Will Not Close (Must be Ended)"
Symptom: After upgrading Symantec AntiVirus, shutting down NT4 (SP6) will hang, and get a pop-up window saying the OleMainThreadWndName will not close (End, Wait, Cancel). This occurs twice before NT4 will shut down successfully.
Solution: Recent changes to support Windows Security Center introduced a new dependency on the code as defined by Microsoft (KB 136885). The code has been corrected to resolve this problem.

Anway, the fix does work. Hope this saves someone a nasty surprise on a Friday afternoon.