Okay - still a bit mysterious, because though it explains some things it doesn't explain others. I'll add the ability to upload URLs sometime down the road - in the meantime, you can always put a copy of any image being displayed in a browser onto your own computer by using right click to copy it, then pasting it into a directory on your own machine.
Thanks for helping me get to the bottom of this. Looks like I'll need a few more clues. So far 2 out of 11 people have had a problem.
I've never tried to get into and modify others profiles,...
I wouldn't touch a profile without a good reason. I used ftp to download your image directly from the server, edited it, then uploaded it again. Probably just as ethically questionable, but that's my story and I'm sticking to it!
Is the black square what you'd like? If so I'll put it back - and we'll change your ID to Darth Admin, moderator of the dark side.
By the way, changes to avatars take effect immediately - you don't have to wait for message pages to be regenerated.