PS: I am using the current version of WordPress.
I am encountering a similar problem; I cannot edit a long page, either. Only, in my case, WordPress appears to let me edit this page. Yet, when I go to save it, I get a blank “page.php” screen. (Other, smaller pages can be edited with no problems.) I’ve tried this in Flock, Safari (Windows), and IE so far; the latter gives me a 406 error (“not acceptable”).
The last time I was able to edit the page successfully was two months ago. Should I delete the page and start over again? Or is there a way to remedy this so I won’t have to?