Security program infected

i have avast security, and when i was downloading an item, bells and whistles went of from avast telling me of a trojan and advising to move to chest which i did and it just kept repeating and i kept deleting or moving to chest could not remove it, so i shut the computer down, then after a while restarted the computer,then avast advised memory infected to run a deep scan.As i am watching the scan it was deleting programs which i know are not infected, i shut down avast and ran superantispyware which got rid of a lot of infections, my pc seems to be running fine now, but my question is can a security company get infected, and if so whats the proper procedure to handle the situation, i have windows vista premium 32-bit thank you.

Hello Patch, I dont know if this is what happened in your case but it might be worth a look
*Bulletin* for AVAST users - Windows 7 Forums

thanks mitchell for the reply, thats exactly what it sounds like, false positives i hope avast gets it straightened out, because if i would have left avast to run its course it would have cleaned my files out, tipped the scales...patch41