Avatars plugin - only some plugins showing


We installed the avatars plugin last month and only some of the avatars are showing on a page that request avatars. http://is.gd/54HJp

I have just tried setting up two new blogs and uploaded avatars for the users, and they displayed correctly. But if I update a users avatar (who currently has an avatar but it doesn't display), it still doesn't display. It uploads fine though.

I thought it might have been the case that only blogs created since the plugin was installed would work, but that is not the case.

Are there any issues that you aware of, maybe some server permissions? I and other have tried uploading avatars, and it only seems to work for me but that is not a sustainable solution.

So to sum up - it displays some, but not all avatars, even though users on that page definitely have an avatar.