oh, there you go...mod_security (or something simular) screwing things up...nothing you can do about exept for contacting your host's administrator...
Good luck.
P.S.
Can you do the following:
1) right click on settings link in ACP -> click on "open in new window"
2) go to file menu in your browser and save the page as html
3) pm me with a link where you download that html page. I'd like to see what exactly is matching the security filter on your server, maybe its possible to avoid it...