I'm trying to set up multiboxing on my computer, and although both of my fully upgraded original accounts can create new characters with no problem, the account upgraded to lich king and the two trial copies just freeze and say "non responding" before loading new characters for the first time.

I'll add it does this with these accounts even if it is the only account running, its not a problem caused by multiboxing per se.

A clue--when I force close it, the message says "World of Warcraft Retail Not Responding" rather than just World of Warcraft Not Responding... does this mean anything?