[Plugin: Regenerate Thumbnails] Doesn't affect thumbs anymore :(

Hi there!
Your nice plugin worked for the first time perfectly, but then – when I decided to change thumb size for Jigoshop again – it showed that resizing succeed but nothing changed 🙁
Even worst, thumbs became blurry (same sized!).

Is it possible to solve it??

I don’t want to re-upload all my products aah~ T . T

http://wordpress.org/extend/plugins/regenerate-thumbnails/