Multitap Problems

Having problems with the multitap keyboard. I have selected multitap in both the options/keyboard menu and also in the setup wizard. When I open an application the multitap key board is there but does not function the way it is supposed to. If you try to get the third letter on the key by tapping three times you will not get the third letter but the first letter three times. I can go back into options and multitap is selected so I select suretype, save it then reselect multitap and save it. This will make multitap work for a while but it will revert back to the malfunction after a while. i returned the phone for a replacement and the new one does the same thing. Any ideas?