Thanks for your opinion henry265, I see it similarly.
lickthetoad: I hope you know that plugins and themes you find on WP.org are free. Some of them are being developed by people – like me – who work in the web developing industry and have lots of clients from different parts of the world who just have a higher priority when it comes to updates. If you expect that everything runs out of the box after every update, you should consider paying for the service.
Even though my plugins are free, I try to put a high level on quality in them. But bugs can occur – that’s the nature of software, especially when you work with many version control systems like SVN at the same time.
If you want to support my work and work of other developers, you can download a modified version here and replace it with the old one. I didn’t have the time to run a whole bunch of tests, but this version should eliminate the error, and if it works for you, I’m going to release a hotfix the very same day I get your response. Maybe this amount of support will let you think about if Thumbnail Cleaner is only worth 1 star.