From the free AVG forum

If you suspect a file to be a false positive. Test the file at [virusscan.jotti.org] and if it is a false positive, archive (zip, arc, tar etc) the file using a password and email a copy to virus@grisoft.com with a brief description as well as the password you used to archive it with.

If it is a false positive , turn off hueristic scanning for the time being. When Grisoft adjusts the virus defintions you can turn it back on. If you are unable to still test/email the file after disabling the hueristics, you will need to temporarily disable the Resident Shield.

. Restore file from Virus Vault noting its path\filename.
2. Temporarily disable the AVG Resident Shield
3. Test the file at Jotti
4. If found to be not infected, report it to Grisoft in an email
5. Re-enable the Resident Shield and Grisoft should update it soon ( usually less than a day but it varies )

Go back into AVG and open the Virus Vault... the "trojan" ( if it is one, at this time we are making an assumption that it is a false positive but only testing can say for certain ) should be listed there... it will also list the original location of where the file was located... write down the location and filename that it shows you... something like ( this is a fake example ) ... C:\Program Files\Google Desktop\somefile.exe ... highlight the entry and select to restore it to its original location.

Disable the AVG Resident Shield from the AVG Control Center

Now, visit the Jotti website that was mentioned, click the browse button on their website and browse to the file you wrote done the location to earlier. This will upload the file to their website where they will test it with many antivirus programs. If only AVG detects it as a threat... then that indicates it is a false positive and you should follow the other instructions for reporting it using email ( archive the file with a password, email the archive and tell them the password you used ).

Now, re-enable the Resident Shield and wait until Grisoft has corrected the false positive, usually this will happen by at least the next day if not sooner but the time will always vary some.

If after that you still have problems... use the System Restore to restore to a point just before the problem showed up.