WP problem: Upload quota doesn't decrease after removing photo's

Hi Guys,

Please help me! I'm having a large problem with my WPMU installation. It seems like removing picture from the media library, doesn't decrease the used space for the site. I recently discovered after activating upload quota for pro-sites, users started removing images and contacting me why the upload quota is still reached.

I tested this on multiple sites and if I permanent delete all images in the library the used space is still the same 76 MB.

At this point I have no idea what to do! Any help will be appreciated?

Thanks in advance,
Pieter