Flash update triggers trojan alert

Windows 7 Pro SP1

Firefox and Chrome

AVG Anti-Virus

I tried getting the latest flash player update for Firefox and everything went fine UNTIL the installer tried to open Firefox, at which point AVG locked everything except my keyboard because it had detected trojan IDP.ALEXA.51 in the installer and would not allow me to anything but click ENTER to allow AVG to do as it pleases. I duplicated this THREE TIMES even downloading the installer from Chrome.

I'll be testing this on my other PC which runs XP Pro SP3.