Could you paste the name of the detection from AVG?

I am guessing it is detecting it in your cache.

See Firefox cache file was infected with a virus for more information and how to clear your cache to most likely resolve the detection.

Note: It is unlikely that you have been infected.

i did post what the infection said in the description above - infection - virus found spam yes its picking it up in the cache yes i have cleaned the cache out a couple of times an it still happens. while i am fairly sure my computer is not infected this should not be happening

Well its been fixed, no longer happening, i did contact AVG about it.