All of a sudden one of my 2 remotes stopped working. Tried reprogramming, changing battery - nothing seems to help. The other remote, wall pad and password enabled entry are functioning normally. This is a Craftsman model. Will appreciate any help / solution. Thanks.

Learn button or DIP switches?

Used Learn button to try to re-program the remote - Didn't work.

What is a DIP switch?

DIP's are Dual Inline Package(usually 8 or more tiny switches), if you have a Learn button, you don't have DIP's.
Will see if I can find additional info.
Swap batteries with a known good unit and check the results on both.

Look here for some examples, enter your model, most are similar, holding learn button down too long may erase all codes. Follow the procedure for your model. Good luck.
How to Program Genie and LiftMaster Transmitters - YouTube (http://www.youtube.com/watch?feature=endscreen&v=7USIB7QaMwI&NR=1)