Here is a fun glitch you can do in Forge World where you 'die' in a way that doesn't kill you. Hard to explain but just know that you enter Hyperspeed and fly through the map to a point that you designate. Check it out! YouTube - Halo Reach Glitch: Hyper Speed in Forge Mode
This is actually pretty similair to a glitch me and some friends noticed. If they're at all related, then what probably happened is one of your "bodies" in Forge died, while the other one was still alive. The game can't respawn you, but it can't let you live either. Nice find.