Firefox WinXP/Win7 can't save campaigns

joomlamailer version: 1.7.2
Joomla! version: 1.5.25
PHP version: 5.2.12
MySQL version: 5.0.77

While creating a campaign on Firefox 9 on windows xp (and win7), pressing save hangs the screen with a never ending saving animation. The error console on firefox says "g.win.document is null" and then it points to "/plugins/editors/tinymce/jscripts/tiny_mce/tiny_mce.js"

Any help on how to fix this (other then just disabling tiny mce) is appreciated!

(this works fine on Chrome, and IE, and other browsers I've tested)