Adding new classes works so-and-so

Hi!

I’ve been using WordPress 2.5.1 for a while now. Everything worked well, but recently I’ve had trouble adding new categories. Adding categories and link categories works, but the screens don’t refresh. For example, if I add a new category in the “Manage Link Categories” screen, nothing happens when I submit the new category, but the category is created.

Same happens when I try to add a category from the new entry screen. A category is created, but the category list doesn’t refresh.

I’m using Firefox 2.0.0.14 on OS X 10.3.9. The system worked well before, this is a new development. I checked with Firebug, and the AJAX code returned seems healthy.

I wonder if it’s a question of too many categories? My blog has 398 categories and about 140 link categories.