Spawning halfway in floor and cannot get out (without breaking the block)

When I first started up the world and converted it and all that. I spawned into the floor and was glitching up and down. I could break blocks but I only had my hands so it took about 3 minutes to break an iron block. The thing stopped after breaking the block below me. I know this bug was on previous versions before when spawning in single player. Because this is an older map and was converted. That may be the problem.
Steps to repeat:
1. Download the mob arena 3 map from here:
http://www.minecraftforum.net/topic/1291016-suradvparpuz-minecraft-map-mob-arena-3-with-redstone/
2. Send it to saves after getting it out of .zip file.
3. Run the world in 1.7.5 (Or 1.7.6)