Possible Trojan...

I booted up my computer tonight and was prompted there were updates available for NAV so I downloaded them and installed them. As soon as they were finished installing, I was imediately prompted the following messages from NAV:

C:\WINDOWS\autoupd\autoupd.exe
> Backdoor.Trojan

C:\WINDOWS\autoupd\upd.exe
> Trojan Horse

I checked the location, hidden files shown, but those files are not there. I did a search on Google for them but got nothing except info on an auto updating application file. I killed everything and did a full virus scan but NAV found nothing, and I have no quarentined objects.

I am confused on what to do. Should I be worried or is this a false alarm?