it does only occur when a lot of images are loaded in
Have you tried dumping in-built animimages and using arrays of single images instead? Also (and I'm sure you've probaly done this but let's be thorough) do check that the type fields you pass to DrawImage are ints and that the requested image isn't of the bounds of the animstrip. I know you're probably right and it isn't working properly, but I can't discount the possibility that the 'working' PCs are actually failing improperly from my comfy sofa.
But yeah, before writing your own pixel collision routines it would be a good idea to see if you can keep ImagesCollide by losing animstrips.