i think the NIS is doing its job well.
i'm a NIS user for almost 1 year, and there is NO virus attacked my laptop.

in fact i feel NIS scanning is very sensitive and good. there was once that i scanned my thumb drive with my bro pc (running on kaspersky) it detected a few viruses. then i perform a 2nd time scan with NIS it detected more viruses that is hidden.

and the 2 files that u mention i think its normal to have it as i check Win XP, Vista and 7 also have the same thing.