said by HA Nut
:jbob: Pure speculation on my part

but I believe NOD's real-time component (used to be AMON) doesn't scan those downloaded files until the downloads are complete. I've always had delays on immediate accessibility of large downloaded files with NOD... even with current 2.7.
In this case I think the culprit might have been IMON rather than AMON. I use IMON now with NOD32 but have HTTP Checking disabled. When I was testing the RC I left it enabled to test. Without further testing however I cannot be sure what the issue was.