I have the same issue with Symbiostock image processor. Sometimes it works just fine but for the most times I get the same broken images.
I suspect that DreamHost uses outdated version of ImageMagick binary. I installed latest ImageMagick binary and built a PHP module imagick.so for it. (in my local path)
But DH php already using its own extension which uses old ImageMagick binary. Could somebody point me how to force PHP use my custom built module?