I've had several crashes in PhotoPaint today, to the point where I had to abandon X7 and go back to using X6 (which worked like a dream).
I was having to crop several large scanned illustrations (all about 4,000x3,000px RGB 24bit TIFs), all with very ragged areas, but all on white backgrounds. This was my method:
This was usually when I had a crash although the program slowed dramatically after clicking with the Mask tool in the white background. Either the program froze and I had to manually close the program or once the crash was caught by Win7 which sent an error report to MS and closed the program automatically.
The same method in X6 worked perfectly even with several of these large images open at the same time. X7 couldn't even cope with only one image open.
I'm currently working away from my office on a Win7 32bit laptop with 3GB RAM.