Mechanic Q: how much would it cost to fix the anti=theft system??

my car starts only sometimes.. when it doesnt start the theft on the dash board flashe constantly and it would not let me start the car. i have to wait for like 2 or more hours to try again. i tried puttin in a new alrm but did not fix this.. i tried to get a new key but they told me they could not program the key. can someone help me please???