i too have been having this exact problem, in intense AE missions, standing around doing nothing, and yes in the character build screen. crashing to the desktop.
i can point it to the patch right *before* issue 14 was released, the day before to be exact. my first crash ever in COH was that day.
ever since then my game crashes so often i want to hurl my monitor through the window. i have also had some other strange costume related issues.
i know it isnt related to system specs or driver versions, im a senior support tech with Dell and i have already done all the PC-related maintenance that would cause a usual lockup of this nature.
my system is running as such:
MSI mobo
AMD 5000 black OC'd @ 3.0ghz per core
Dual Nvidia 8600gt OC edition also MSI
and 4gb of ram
running Win XP 64bit
all drivers and windows updates are current.
from all the other posts and from my own testing i beleive it is a latent issue with the game since the patch as it doesnt seem to be related to load, content, and/or time in game.
i have however noticed it seems more frequent in the zones chocked full of people: Atlas Park, AE buildings, Steel Canyon.
i have never seen it crash in the less populace areas; hollows, faultline, etc.