ImageShack (partial) rule breaks Flash-based picture uploader.
The "ImageShack (partial)" rule that appears to have been added in 3.0 development 2 of HTTPS Everywhere breaks the Flash-based file uploader. Anything the user attempts to upload with this will fail.
Solution is to disable the rule and make sure that you're on the HTTP version of the site.
Trac:
Username: DaemonFC