First, lets lose the language guys.
I had the very same problem after upgrading to 4.2.1. If I have groups in my address book I have problems dialing from the home screen. When you press a letter that is the first letter of one of your groups you'll get this error. Usually it would clear and go away. However, at one point it stayed and not even a battery pull would clear it.
I had to us JL_Cmder (in my sig) to wipe the handheld and reinstall the OS. There are instructions in the following post. If you can get a backup made then great but if not you'll be left with a fresh BB when you are done with this procedure. http://www.blackberryforums.com/gene...ipe#post414629