Looking at Reports > Recent Log Entries, the message is "The specified ImageMagick path /usr/bin/convert does not exist". However, I've configured my ImageAPI module to point to /usr/local/bin/convert to find convert, and this is saved correctly according to the config screen. It shows the version information correctly. I try clearing it and retyping and saving it.
Using phpMyAdmin, looking in the variables table in my database, I see only a variable "image_imagemagick_convert" is set correctly but there's no "imageapi..." variable.
I copy the record and change the name to imageapi..., reload everything and it works.