I take it you have the AK2.0, as opposed to the AK2.1? If so, I'm afraid you have one of the bad cards. The same thing happened to my first AK2- it just freezes when ever you try to load anything or save the config menu settings, right?
You could try contacting your retailer for a replacement, however, some of them are not very helpful. If you have problems with the retailer, you can go straight to the manufacturer. Many people on GBAtemp have mentioned that team Acekard are super-friendly and they will send you a new card if you write them a nice email explaining your troubles.