Problem with Image Uploading (maybe thumbnails generation)

Great plugin, with a lot of options.
But, I don’t know why, I’m having problems when it’s active: I can’t upload images in my Dreamhost Shared Hosting. Actually, it’s happening in localhost too. When you try to upload, you get a “Http error” message.
When it’s inactive, problems dissapear.
It took a lot time activating/deactivating plugins to know wich was having problems. It’s happening with last version but also with some others.

http://ww.wp.xz.cn/extend/plugins/feedwordpress/