Latency/ping problems in game/slow internet

Well, i need help from you braniacs at MG again. Ive been having very very bad ping/latency while playing wow, and my internet is just a lot slower. I get about 4000 ping in wow, and when i turn off my antivirus and firewall it goes down to 1300 ish. But ive never had this problem before...I use mozilla, and when im trying to do anything, it take forever to load pages and pictures and to send and recieve data from a site (such as this). I dont think its a virus, im sure i would of caught it if it was...( i may be mistaken though) If i Restart my computer, my internet is as it use to be, but it seems sometimes if i start WoW it slows down alot... I really need help because i cant do anything in WoW...=( Im running Windows xp pro i have avast for anti virus and a-squared for a firewall...Really need help guys D: