I don't have a propane bar-b-q, but I've been told that a very common problem with them is that the gas pipes that go to the burners are just the ideal size for a wide variety of spiders to build webs in. These webs get clogged up with other dead bugs and cut off the gas flow.
Before you start replacing the regulator, take the burners out and check them for spider web blockages.
Also, it doesn't have to be something as flimsey as a spider web. Lots of bugs will build a nest in the gas tubes going to the burners of your bar-b-q, and any of those nests will be sturdy enough to prevent proper gas flow to the burners.