This was done on a fresh install of Minecraft as I've just moved to a new computer.

What happened:
Upon my first death, when I clicked respawn, the game froze for 10-30 seconds.
After this, a Windows firewall popup came through asking if I wanted to allow Java on this network (I believe this is the source of the issue).
Then I was given a disconnect error, and returned to the Multiplayer server selection screen (despite the fact I was playing on Single Player).
Upon reloading, I found myself at the position of my death, with all my items intact, and duplicates of my items on the floor around me, as if I had died.

What I expected to happen:
If the initial error can be caught or prevented, (by not attempting to communicate over the internet for example) I would expect to die as normal and respawn.
If not, I would expect to be returned to the Single Player world selection screen or main title, possibly with an error message.
Upon logging in after such an error, I would expect to either be dead, be at my spawn point with no items (and ideally be capable of retrieving them from my death point), or be at my death point with my items on me but none on the floor.

I appreciate there's probably nothing you can do to catch the firewall popup once it appears, but preventing it initially or handling the error better would be good.

Steps to Reproduce: - please note I have not tested this, it is suggestion only.
1. Clean install, notably do not have any firewall rules set up for Minecraft/Java.
2. Create a new world in SSP.
3. Die.
4. Attempt to respawn.

Not sure if it's relevant to the error, but I had a bed spawn set.
No images sadly, as I didn't think it was a big issue until I noticed the multiplayer screen and duplication of items.