So the reason my server has been crashing is because some weenie with the IP 188.8.131.52 that traces back to India has been hitting my title generation script, many times a minute, with requests to generate 13 digit numeric string images. I had 100's of thousands of cached image files! Afterall the script was designed for my own use, not the abuse of some dickwad.
Blocked and banned. I'm keeping an eye out for hits to that script not coinciding with page loads, and will block aggressively.