is 640*480 a ^ 2 texture size (loading screen) the strange thing is it works perfect on my gforce MX 440
No. Powers of 2 are 2,4,8,16,32,64,128,256,512,1024,2048, 4096, etc ( I could go on for a while )
Blitz won't usually kick up a stink, it'll just resize the texture to 1024x512 ( which is kinda blurry and wasteful ) but it usually won't crash.