I just spent 20min. troubleshooting some ImageCache settings in drupal that could have been easily solved by paying more attention to readme.txt files.
I created an few imagecache profiles. One for my thumbnail images, and another for the full sized images. I wanted scaling and cropping on them so they all turned out the same size for a nice gallery. Everything seemed good except my images weren’t being created. I got a 500 error from the server every time I tried to preview one.
The error was a simple one, you need to turn on an image processor in Site Building -> Modules. There are two provided out of the box, GD2 and imagemajik. Once I checked the GD2 box, everything worked. I like simple fixes, but I hate wasted time. . . The readme file is pretty clear about how to make it work.