Image problems

Hi guys, hopefully this can be solved.

My site is having an issue with uploading images, either via flash or html, and regardless of the OS/browser (tested in OS X and Win 7 with chrome, safari, ie & firefox).

Basically no uploading happens. It jumps to finished in a split second once you choose your image and then it finishes with a red 7 where normally a thumbnail would be. It only happened for the first time yesterday, which means it was working fine even after upgrading to the new version previously. I’ve no idea what’s going on and google is no help either.

Server is running Windows if that helps.

Thanks