I've experienced this several times, I would have a LD, "wake up" in my house somewhere, and I'd literally be unable to escape the house. I can easily phase through interior walls and doors, but when it comes to a wall or window leading outside, it's really like an invisible force is keeping me in, and if I push a bit harder, the force pushes me back, kind of like I'm trying to push through a big elastic band.
Only once I recall actually making it through (without changing the scene/teleporting like I would otherwise do), once when I reminded myself that this is my dream and nothing can stop me, then floated through the wall with little resistance and made it out.. Does anyone else have this weird little issue or know why it might be happening? =/ I never felt like my house was a prison or anything like that, lol.

p.s. for some foolish reason I hardly ever even think of doors, mostly because I find it so fun to phase through things, perhaps I should really consider doors XD But would still like to solve this little issue.