WYSIWYG errors...

I've searched and searched and can't seem to find an answer to my problem, or even someone else asking the same question. If it's out there, forgive me and please direct me to the proper thread. Otherwise...

I recently installed Drupal 6 and was having no problems until I started entering content via the WYSIWYG editor. Every time I submit my changes, I can see that the editor switches off "Rich Text Editing" right after clicking "submit" and then it appears as source HTML on the node. I've never had this problem before in the 3-4 years I've used Drupal so I'm not really sure where to begin. I've tried various browswers (IE and Chrome), both have the exact same problem. I tried a diferent editor (FCKeditor and now Tiny). Both with same results.

With my luck, it's probably a matter of simply unchecking a box somewhere, but I have no idea where this mystery box may be.

Any assistance is appreciated.