I had a problem since 3.2 that when I logged on my druid, it would immediately freeze and DC me. Im not sure what causes it, its actually a WoW client crash, but no alert for it. The fix I used in case anyone has this issue is to do the following:
Log on another character (diff from the one you've been DCing with) with all addons disabled.
Log off, then enable your addons and log back on.
Log off and relog the character that was crashing WoW.
That seems to work, just thought id help in case anyone else ran into this.
As best as I can tell, this is a bug with 3.2 and Dalaran at peak hours. Since I home my druid in Darnassus now, I havent seen this problem return. It only seems to happen if you try and log on in Dalaran when theres tons of people on.
When that happens to me - the culprit seems to be Questhelper. If I disabled that one I could get on. Could be something unique to my combination of addons.
I dont use Questhelper, so i really dont believe it to be an addon.