Inventory Resets On Relog

[CopperWolf]

I went afk from ~3AM to ~11AM on March 19th. After I got back from my AFK, every time I log out and back in I appear in the spot that I afked, and my inventory is reset to what I had on me during the AFK session. I have (without success) attempted to fix the problem by:
-Killing myself in-game. No effect.
-Restarting my client. No effect.
-Breaking blocks around the spot I appear. I just appear at the location in midair and start falling.
-Placing blocks to occupy the space I appear. This caused me to appear inside the blocks and be pushed out immediately.

The exact location I appear at is:
XYZ: -4359.300 / 80.00000 / -1342.542
I appear facing West (Toward negative X).
The exact contents of my inventory every time I log in are:
Full iron armor, 22 planks, 5 seeds, an eye of ender, 12 sticks, 3 iron ingots, 1 mappad, 1 powered rail, 1 water bucket, 2 minecarts, 12 stone slabs, 23 gold ingots, 1 diamond shovel, 2 iron axes, 1 diamond sword, 1 diamond pick, one bow, 9 ender pearls, 28 glass, 4 torches, 9 bread.

This is somewhat game-breaking, as I will lose any items I put into my inventory unless I remove them before relogging (so far I have not lost anything substantial to this), and any items I put into chests or other inventories become duplicated.

I have placed 1 instance of my inventory into a chest so that if fixing this problem deletes my inventory, I won't lose any of my items. Aside from that chest, I have thrown out all duplicates.

-CopperWolf7