Thing with definitions, sometimes the guys/gals get them wrong - this has been known to happen with Kaspersky, Symantec amoung many others. Sometimes the mistakes are very serious:
http://news.com.com/CA+antivirus+del...ht&tag=nl.e433
For a server, but you can see the problems it can create. My advice would be to
quarantine files and not delete until you are sure they are infected. This way if it is a mistake you can replace the file, incidentally quarantined files are completely safe.
If you come across FP, best thing is to report to the program makers, that way they can get the problem fixed, helping them, you and others users - either do this by email or use their forums (if they have one).