Karizma plus control panel with lcd keypad?

I have replaced the battery following a low battery warning on the keypad,all was going good after powering up but now it is showing checksum error/checksum error then failed and has now advanced to fault with the keypad in what seems to me to be in a lockout stage.
I spoke to ade yesterday who were not very helpful and also following a net search i turned up nothing regarding checksum although I do believe it has something to do with it's memory.
Has anyone else encountered this error and if so how can it be overcomed.
Heres hoping and thanks.