This has been happening for a very long time (about nine months), and I am a little surprised that it's still going on. Maybe I am alone in having this problem happen, though I doubt it, since it's happened on more than one computer for me.
The first problem comes with the initial submission - whenever I click "submit", I get a blank white page saying that the server has timed out. Usually, however, if I wait a few minutes, my new submission shows up on my page anyway. So that's not as big an issue.
More recently though, whenever I try to edit a submission, if I click "submit", it immediately jumps to a blank white page, and nothing happens. Nothing changes either. I don't know why the submission/editing system for the art portal is so buggy. Has anyone else had this problem?