I'm been playing a 10 day trial of WOW, and I get "Disconnected from server" at least 3-4 times an hour, sometimes in less than 2 minutes...
I used to have this same problem with City of Heroes WAY the hell back... I ran a positron (or was it synapse...) TF one time where I couldn't stay logged in long enough to do anything after finishing buffs (Speed Boost FTW!!!). I'd drop... try to get back in, rebuff, drop... heh Gawd it sucked... but I was able to stay in the game during the AV fight and got my SO...
As for how it was eventually fixed... No idea... had nothing to do on my end (seemingly)... Pretty sure I had also tried updated drivers, etc... It's possible they fixed it on their side, and this is likely because they did make some netcode improvements AFAIK.
Don't really have any suggestions on how to get this resolved, but like any PC problem, it can be caused by a few of a million things... And it's quite likely, it'll just fix itself (so ta speak).
Ok I do have suggestions... Try your PC at a friends place that has a different ISP... Try a diff server, like Zul'Jin (horde), where you can say hi to Skane (Undead Rogue) : )
Anyways... G'luck... I know how insanely annoying constant disconnects are, and I hope it's resolved soon ; )
If you do happen to find out what's wrong, but your 10 day trial is up, or some shit, lemme know... I have extras, or if you have another email addy, you can just get the referral one set up (again) : )