I am on my second disk and still I have the same problem.
As soon as you try and enter "The Strip" the game locks up and corrupts the Auto Save file.

Please can someone help me resolve this issue?

Its not about your disk pal, all the disks have the same poorly tested, overpriced, junk code on them. I wouldn't waste anymore time returning your copy of the game and just wait for a patch, or if possible return it for a full refund. I live in the UK so once I broke the seal on the game I was exempt from refund, the only reason I still have this game.

Once again, an issue that can be resolved by searching the forums. This is a known bug posted and complained about by countless people.

I'll be nice for some reason today though... Find an "Old Cowboy Hat". You killed the guy for the Debt Collector quest which triggers the bug, so now you need to go get an Old Cowboy Hat and wear it into the strip the entire time you're in there. Bethesda has said this bug will specifically be addressed/fixed in the upcoming Xbox patch (it was already fixed for the PC).

When you say that you're on your 2nd disc, please for the love of God, tell me that you returned the 1st one for a new one, and that you didn't just buy another game. The last thing I want is Bethesda making anymore money on this P.O.S. than they already have... Oh and no kidding, do a search before you post. This problem/bug is posted everywhere.