I Will Never Understand ComputersFollow

Sounds like a problem I was having not too long ago. My druid would be disconnected from WoW at least once per session (even short sessions), while my other characters could go for hours without a single disconnect. Then to get back into the game, I'd have to log onto another character, log out, then log into my druid or it would continue to DC me everytime the game loaded.

I really thought it might be my internet provider since my DSL likes to disconnect whenever the phone rings, but I decided to try deleting my addons folder (instead of disabling them one at a time) to see if that fixed any issues. I kind of doubted it would since I was using the exact same addons for all my characters, but only having problems on one of them. But after redownloading the updated versions of all the addons I could find (and a few old versions of the ones yet to be updated) I can now play the druid as much as I like without disconnecting.

I know you've said you reinstalled WoW completely, but have you tried deleteing any addons? Sometimes even the up to date versions can cause issues. (Heard of an issue with the Gatherer mod DCing people)