Well I just tried your site. Registered as RER and used the referenced URL for a avatar.
Same problem as you have, timeout issue. But I copied the JPG file to my server and referenced it as a avatar and it worked fine.
So it sounds like some configuration issue between your two servers.
Maybe a referrer issue since it looks like the forum is set as a subdomain?
Does anybody else reference a avatar file from your main server to your forum server.
