Does Spy Sweeper read, "Potential rootkit-masked files H9GUFFP6"? A couple of Spy Sweeper users, reported the same detection at the forum below. In their cases, no other scanners detected it, so they posted a HijackThis log to be sure. In both instances, it was said to be a false positive. In the first link, see where the administrator writes in the second post, "H9GUFFP6 is a false positive from SpySweeper".
This was reported as recently as last month.
In the 6th post in the thread just above, the user received an email from Webroot which said, "Your system is free of spyware. The files detected by the RootKit Detection are legitimate and pose no security threat to your system. Spy Sweeper's "potentially rootkit-masked files" detection is not definition based, it is essentially looking for discrepancies between what Windows sees and what is actually on disk. It will from time to time detect harmless files. Click 'Options' > 'Always Apply' > hightlight the rootkit detection and click 'Always Ignore.' Thanks!"
I don't know if the above will ease your mind any, but it's worth considering, if no other rootkit scanners detect it.
Best of luck..