Suggested answer to previous posting from MovableType Support Forum:
it sort of sounds like a browser issue. have you tried clearing your temporary cache and cookies?
it might still be server related if it's cutting your connection off prematurely; but i think it sounds more local machine related.
I just emptied my cache and cookies and I still have the same problem. I'm going to try a different PC and see if that makes a difference.
Update: I tried it on a coworker's PC and the same problem occurred. Maybe it's the company firewall?
This entry also posted on MovableType Support Forum.