It's funny that you say that about letting go on a rope vs. feeling more comfortable bouldering, because I feel rather the opposite. I mean, when I first started, yes, letting go of the wall was a big deal--I think it pretty much always is, those first few times. But now I've been climbing for years, have taken big falls on lead, and I generally don't have problems trusting the rope or my climbing partners when I'm leading or toproping, especially indoors.

But I STILL get nervous about jumping/falling from the bouldering wall. Even when I know there's a mat, that it's not that high, I try under all circumstances to downclimb at least a few moves, and I'm hesitant to make risky moves near the top of a problem because I don't want to fall. There's still this psychological thing about hitting the ground--even when I've only fallen a few feet. I know I just need to practice it more (I don't boulder all that often, really, so it's more unfamiliar). As with anything, practicing the nervewracking things is the best way to get over the mental block.