I admit I picked a later version up there since SMP 1.4.7 was not selectable. Since my friends don't want to update, I'm stuck trying to fix this in 1.4.7.

If an update fixed it, let me know. That said:

Playing in SMP with friends, had two jukeboxes placed in my world - destroyed one with no tool (just hand) and the game crashed. When I reloaded, everything I had built in the chunk the jukebox resided in was gone. All the original terrain was still there, but the stuff I had built was unloaded. The game acts as if the items are still there, as noted by a floating torch in the adjacent chunk, as well as water that would usually start flowing down immediately being suspended against an invisible "wall".

Trying to interact with things I know are there does not work - I fall through where the floor should be.