The icon is no longer freezing after resizing in pre-release 1.7, but the player icon still freezes when you save and quit to title in single player.
The player icon on the map item also stops updating on your first map after creating a new map in another location and resizing it.
To reproduce this. 1. I made a map, resized it completely zoomed out. 2. Then created a new map outside of the area covered by the first map. 3. Then after resizing the new map 4 times (completely zoomed out) the player icon on the first map stops updating when you move back into the area that the first map covers. It also stops updating if you save and quit to title. Once you completely exit the game and come back the player icon shows on all the maps again and will move correctly.
I found this too. I re-created the world with the same seed and went to see what made it explode and every single time it was detonated before anything in the desert temple was interacted with. Finally I found a command to teleport the primed TnT away and went to see if there was any lava generated near the TnT and there wasn't. Also, when you hit the TnT with a tool or your fist it starts to detonate. I also teleported inside of the temple after I created the world to see if mobs had walked on the pressure plate and there were no mobs there either. The seed (-7869274119369579052) The coordinates of the temple are 633, 65, 331 or 633, 53, 331 near the bottom.