I'm getting a 500 error when trying to access the full version of any image. As soon as it's uploaded to the server, it becomes 'unavailable', and each file cannot be accessed/deleted/anything - like Wordpress is holding on to the file somehow. However, any thumbnails work fine.

We have tried:

• Changing permissions on the server
• Allowing media to be put into date and month folders, and to not be.
• Changing the folder that images get put into.

We're running a Windows 2008 install. Everything else seems to work but this. As I mentioned, the thumbnails are all fine. Any ideas?