Ok so i was doing the quest talent pool and i was able to get a few people. i had to get 1 more person but 1st i had to go to the tops casino to get my money from the last one i got. so there i was just traveling to the gate then it says i need a key to enter. WTF!? so now i cant enter the strip anymore and it was saved when i traveled to the north gate.
any help!?

It's a bug. If you go to Camp McCarran just south of New Vegas you can get on the monorail and take that to the Strip. From my understanding if you exit through the doors this will fix the problem.

I also believe that the securitrons guarding the door have a key on them.

i cnt take the monorail because its destroyed from a quest i done. and the securitrons did't have the key.

Try the cowboy hat trick, just get it at the Crimson caravan and wear it, should do the trick