1999 Pontiac Grand Am DOOR LOCKS

I HAVE A 99 GRAND AM GT TWO DOOR WITH A 3.4L ENGINE, WITH AUTOMATIC DOOR LOCKS, I HAVE AN AFTERMARKET VIPER ALARM. THE LOCK WERE WORKING FINE UNTIL RECENTLY TWO DAYS AGO, NOW WHEN I TRY TO LOCK THE CAR WITH THE ALARM, THE ALARM ACTIVATES BUT THE LOCKS WONT, SO BEFORE I ACTIVATE THE ALARM, I TRY TO LOCK THE DOORS WITH THE LOCK BUTTON, I PRESS IT SEVERAL TIMES AND IT WONT LOCK THE DOORS, BUT SOMETIMES IT DOES WORK AFTER THE SECOND TRY. ALSO SOMETIMES, WHEN I LOCK THE DOORS WITH THE ALARM. THE LOCKS WORK. OH AND WHEN THE LOCK BUTTON WORKS, THE LOCKS WORK WHEN LOCKING THE CAR WITH THE ALARM REMOTE. WHAT COULD BE THE PROBLEM, COULD IT BE THE ALARM, THAT IS CAUSING ALL THIS PROBLEMS?

P.S. I HAVE HAD THE ALARM FOR 5 YRS AND IT NEVER HAD THE PROBLEM I HAVE NOW.

THANKS.