WordPress MU

Hello, i tryed to search help here but without results. My problems is fullsize jpg images. Thumbnails is OK. When im uploading images it seems to be ok, but when im trying to add / view fullsize images i can only see this error.

http://myblogpost.net/urheilublogi/files/2007/09/aat.jpg

Problem is only with .jpg pictures. gif pics works fine.
And yes, .jpg is enabled in admin.

Problem is new and .jpg images was working before. Whats wrong? Something in script or in my webspace offer?

http://trac.mu.wordpress.org/wiki/DebuggingWpmu please as well as a link to a sample image would be helpful. The version of GD (mu uses GD, right? I can never remember.) installed as well would be a plus.

Problem almost solved. My hosting company has disabled readfile. Is it possible to modify wp-content/blogs.php file to function correctly without readfile function?

It might be but I've got to admit that's its probably in there for a reason. To be honest though, I couldn't tell you.

Donncha?