I have the same problem with Firefox 3.5 — but it works fine in Safari 4.0.2 (I’m on a Mac)
This just started happening to me today. Used TinyMCE to create table. Everything worked fine. Trouble started when adding images to new rows at about the middle of the table. Was able to recover work from AutoSave, but cannot get this to work. Anybody have any luck resolving this? Using WP 2.7.1 Was working fine with all plug ins, so adding a plug-in did not trigger the problem