TinyMCE not displaying in Firefox

TinyMCE (Drupal plugin 6.x-1.1-dev, editor version 3.2.1.1) wasn't displaying properly in Firefox 3, but showed up fine in IE. Not sure if anyone else has had this particular problem, so here's the fix I used.

In the file tinymce.module, add this after line 217:

$tinymce_mod_path = 'sites/all/modules/tinymce';

The above code overrides the automatic Drupal routine that specifies the path to the TinyMCE plugin files. While it fixes the problem, I can't figure out why this issue was occurring in the first place. Ideas?