First, thank you for the plugin, it's very usefull !
But there is something that, i think, is going wrong:
When you upload a picture as the plugin is activated, you can't edit the original image, you will edit the last (or one of) the new sizes you have just declared.
Here are some screenshots before/after activation:
(i tried another plugin with similar behavior, Additional image sizes (zui), maybe it is a wordpress glitch)