The rule to follow is when in doubt, do a Boot-time Scan or run a scan in safe mode. Errors will occur daily with files in use or that are temporary. Some of the common files are .pst (email) and update packages (virus definitions). However, there are others, but the first thing you want to do is an internet search for the file and its purpose. Second, once you know what program uses it, shut it down and scan the file. If there is still a problem, get off the internet until you confirm your system is secure.