I can no longer save entries in MT4, either published or unpublished.

Last night, it worked. This morning, it doesn't. When I write an entry and click 'save', my browser loads and loads with no change. After about 5 minutes I get a blank screen.

If I log out and in, and then try to create a new entry, MT gives me the option to recover my entry. If I recover it, the article I tried to save recovers fine. It just never saves, published or otherwise. Help?!