Fatal error: Maximum execution time of 30 seconds exceeded in /drupal/drupal6/includes/image.gd.inc on line 190

When starting the module it's looking for published images to convert.

When there are a number (more than 20) images new to the system image.gd is called to create the derived images. This takes up a lot of time if there are numerous new images and that's why the error as described above appears.

A (primitive) workaround for now is to push the F5 button to refresh the page until all the derived images are created. After that you can convert as usual.

I'll have to look into this to solve this issue.