I just purchased the "Dead Money" DLC, and was mystified at how to get access to the bunker that it sounds like it's supposed to start in. No matter how much I play and wander, I can't seem to get the radio broadcast pointing me to the DLC.

A quick Google search seems to indicate that I might have played the game too much to be able to access the DLC since I've advanced the main storyline up to just before the battle of Hoover Dam. Can anyone confirm this? Am I really just out $10 unless I want to abandon my 60-ish hour save game and start all over?

Unless you're actually AT the dam battle, you can go wherever you want.

I played it with my character who I made a save with right in front of Caesar. (Final quest all ready to go.)
So I dunno how one can be "too" far ahead in the quest line.

You should actually be fine, I had a save just before the Hoover battle when I first got DM, I did the same too. Couldn't work out for the life of me as to how to get it working. After a while it just popped up though and the bunker was open... :S

Not sure if it was anything specific I did though, just random I think unless you have it load from the beginning, at which point it usually fires up about the time you first leave the saloon in Goodsprings..