Did you ever figure this out? I'm having a similar issue with the free version 6.0.1000. It scans between 2,500 and 4,000 files around 1 AM every day, or later in the morning if I shut down before 1 AM. The quick and full scans are not marked as scheduled. There's nothing in the Windows Task Scheduler either. Unlike the poster, nothing appears in the scan logs. I only see the activity in the traffic history when it spikes.