The problem is probably the same as when you try to change your username, namely that you cannot change it to something which has different capitalization, but for the rest is the same. Meaning you cannot change "blabla" to "BlaBla" or "blaBLA" etc.
So you can try to rename your category from "ask43.ORG" to "ask43.ORG.temp" (or so) and then rename this category to "ask.org"
Ivan
-----
Iyengar Yoga Resources / GT Plugins
So you can try to rename your category from "ask43.ORG" to "ask43.ORG.temp" (or so) and then rename this category to "ask.org"
Ivan
-----
Iyengar Yoga Resources / GT Plugins