WoW Lag Problems (Tried everything!)

About 7 weeks ago, I started having difficulty playing World of Warcraft. I've been playing since release in November of 2004, and just started having this issue around June 10th. Basically, almost every character in-game blinks around the screen or runs in circles, indicating what normally is considered packet loss. My latency is around 180, which isn't bad, but before thisproblem started, I was averaging between 50-90 MS. However, my tracerts to each server I play on look fine, without any packet loss. I have tried EVERYTHING, and still cannot fix the problem. Even Blizzard has given up on me. Here is what I have tried:

Ran spyware sweeps coming up clean (Spysweeper mainly)
Used 2 different PCs
2 reformats
2 apartments (although in the same complex)
4 modems
3 Routers ( Problem occurs with and without use of router)
2 ISPs (Adelphia and Qwest)
3 Network cards
3 Sound Cards
3 Graphics Cards
All the recommended settings from Blizzard (full duplex, checksumming off, etc)
Tried various firewalls, disabled firewalls, etc.

I can't think of a single factor that could be causing this. I have changed almost everything possible, and I still have this issue. WoW is the only game that has this problem. FEAR and Quake 4 run perfectly, with pings around 60-80 MS. Please help!