I'm using version 4.0.13 - it's a fresh install... heavily modified.
I used the following code from Boomer to use two email fields to try and minimise the idiot factor when users register, works like a charm...
http://forum.x-cart.com/viewtopic.php?t=10086&start=15&postdays=0&postorde r=asc&highlight=emailtwo
However I'm not sure I've got in 100% right as the validation is stopping the registration process in the check out, I've probably overlooked some of the code to use. I will let you know how I go.