I'm using Keyclone,

Specs are as follows

Vista Ultimate 64 bit SP2
8 Gigs of DDR2 ram
Intel Core2 Duo 3.00 ghz clock
Nvidia GeForce GTX 295 (DX10)
I made two tauren shaman, put one on follow, accepted the quest in Mulgore to kill the Plainstriders, ran for about 30 seconds in the direction of the Plainstriders, and the main instance of WoW (the one that I was controlling as a main) locked up

has done this three times.