This happens to me on long dreams sometimes. I'm haveing the dream (not LDing) and i get pretty far into it when i shut my eyes and can't open them again. I try really hard to open them and i just can't do it. After awhile of trying say 2 3 minutes i get them open and the dream picks up where it left off.

Any idea what this is and how to get out faster or better yet, prevent it?