Mystery of the missing category function

I’m still experiencing the category issue while on the “write post” page. This entry is mostly for me to show WP support what’s happening. I’m emailing them again since I haven’t heard from them yet.

As I understand it, this is what we’re supposed to see when we’re on the “write post” page (as shown in the WP FAQ) *I’ve circled the part that is missing from my page*:

Instead, this is what I see after I click the “Add New Category” link. Notice the “Loading” link on the left… it never changes. The only checkbox that shows is next to “rants n raves”, which is my default category… and it’s not checked by default, I have to manually check it.

Additional information: I’m using Widows XP, FireFox 3.0.1, and all the applicable settings are enabled (that I know of). I’ve tested the dashboard and “Write Post” page in IE 7 also, with the same exact results.

Possibly related problem: When I upload pics to the Media Library, I cannot close the lightbox using the “x”, I have to navigate to a prior page, losing any edits. I had to upload, and get the image url from the media library, switch to HTML, and insert the image url that way.