I seem to have a similar problem.
When I start up this particular computer (something I don't do that often, now 5 days since last start-up) NIS immideately starts an Idle Quick Scan. The problem is, I think, that NIS doesn't recognize 'idle'-state, but starts its Idle Quick Scan even if I am working with the computer. The Idle Quick Scan doesn't stop when I use the computer. The Scan Time for Idle Quick Scan is reported to be 07:26 (~5500 item scanned). Right at startup also Automatic LiveUpdate (Duration 3:32), and Norton Community Watch (4:23) are executed. Norton Tasks reports correctly that none of these three jobs were "Ran During Idle". IMHO it is quite annoying that I must let NIS work for some 15 minutes before recources are freed up for me to use.
What solution do you suggest? Why doesn't NIS wait for the computer to be idle?!
I've configured the NIS Idle Timeout to be 20 minutes. My NIS is up-to-date, version 17.7.0.12.
[edit: Clarified subject.]