You can always check elsewhere if the file is a trojan.
But I guess it probably isn't.
It is said that McAfee does not allow whitelisting or exclusion of files for scanning, except for enterprise products. If McAfee concludes that the sample you sent them is a false positive, they can provide you with an extra.dat or something like that, in which case the false positive will not occur again.
I have SecurityCenter 9.3, and I don't know if this works in an earlier version: (please keep in mind that my software isn't in English so I'll translate as best as I can): doubleclick on the SecurityCenter, advanced menu, configure in the left pane, computer and files, advanced tab of (anti)virusprotection, list with trusted items, and there you can add a trusted program. (I have never used that option.)
Another AV ? There are plently, the website
www.av-comparatives.org can give you some information, but remember it's always best to trial a product before buying.