First, thanks for a fantastic plugin. The setup was easy as well as customizing the size of the thumbnails thanks to your tutorial.
However, we are experiencing something I cannot fix. When we first installed the plugin the thumbnail size defaults to 150x150 as usual. After we changed the settings, new thumbnails started showing up correctly. BUT...we noticed some of the thumbnails were displaying the wrong size (stretched). It appears this affects thumbnails that were previously displayed (before the size change) and the plugin is "locked in" to picking the 150x150 version.
We've cleared all caches and rebuilt all thumbnails already to try to correct it to no avail. Here is a page that clearly shows the problem:
The first two thumbnails reference the 150x150 thumb, while the third one displays the correct thumbnail. I have confirmed via FTP that the correctly-sized thumbnail does exist for those that are being referenced wrong.