There are many reports of failure for the Mazdaspeed6 GT keyless entry/ignition system. Most people report that one of the buttons stops working (usually the trunk). If that is the case with yours, just take it to the dealer and they will fix it for you.
If you have a standard keyless entry system where you need to press the button on the keyfob to unlock the doors then that is a different issue...of which I haven't seen any reports. In any case, take it to the dealer if it is still under warranty.