Here's what xBlackMambax 81 said...
"basically when u freeze yourself, the in-game timer stops while everything else in the level keeps going on. the only downside is that freezing urself corrupts ur file, so the rest of the level has to be done in 1 segment."
Edit: Here's a video of one of those freeze thrower glitches.
http://www.youtube.com/watch?v=xhzwiOe4h34