Stressing your system should never cause a WoW to exit. Sounds more like something is getting out of kilter between ISBoxer and that WoW for some reason, especially since it's the same one and since it won't resize properly. Just a WAG, though. Without debug info, it could be anything from video drivers to bad RAM to a bad sector on the hard drive where that WoW is installed. PM Lax and see if he can get you a debug build to try out. Might at least rule out ISB as having seen any bad data or unresponsive windows.