Rightclick Is Not Woking After SP1

T7700, Business This problem arose since SP1, and persists after previous advice. It's the only issue amid several benefits, so I would like to fix it rather than roll back. When rightclicking a desktop icon, I'll sometimes get nothing. Rightclicking again produces a NOT RESPONDING and then a white Explorer reboot. Then all is well... until next time. It's unpredictable -- I cannot define the circumstances that will reliably cause the problem. SFC /scannow in safe mode found zero faults. Various malware checks found nothing. I installed the ShellExView tool but learned little and solved nothing