Not sure if this has come up already, but I recently was having problems uploading photos on my facebook business page and would get a "HTTP Error 500 Internal server error" and would be directed to an error page. Facebook FAQs said it may be a server error on their part or a flash/cookie issue on my end, but nothing seemed to work. It didn't occur with IE only chrome and only on my computer as I tested it on another. The on thing that I've changed recently was I added Ghostery as an extension to test it out and get a feel for it. I removed this extension and the problem went away immediately.
I'm not sure if it was just the extension or a combination of things, but this fixed the problem for me and I have seen more people on the facebook error report page having a similar problem with their photos so I hope this may help someone if they are having similar issues.