/spawnpoint or beds won't set your spawn point

When using the command block to set your spawn or sleeping in a bed, when you die, you will spawn at the original spawn, and in the chat it will say: "Your bed was missing or obstructed".

11.11.12: I tried the same on some of my other worlds, and I had no problems.
The map was created before 1.4, in 1.3. Also, when I tried it on the surface (the problem is in a cave), it worked out fine...

11.15.12: Updated to 1.4.4 today, still not working...

11.22.12 Tried in 1.4.5 today, had the same problem... I wonder if it has to do with the location of it, i'll try moving my dungeon (thats where the commandblock is) further down or away from the previous location.