I usede Quick.Cart 0.3 which works very very fine on my own server while i am testing.
I have now uploadet my Quick.Cart to my provider azero.dk and the system actually works very fine. But......
When i try to upload pictures for my products i can only upload *.BMP picture... JPG or GIF pictures will not upload. I have talked to azero.dk but they dont know why it wont work..
My first thought would be. CHMOD 777, but that cant be the problem since BMP works. They use PHP 4.3 and GD Lib version 2.
The first thing I would say would be that you dont have the jpeg/gif plugins for GD... but thats already been said, and aparently you do.
Still, perhaps they're not working properly. Perhaps you could try downloading them again and replacing the ones you have right now? (google php GD and go to the man page, it'll give you the links)
Otherwise I cant see why it should prevent you from uploading jpgs and gif but still work with bmp :S.