This must be due to a corrupt game. I found an older saved copy of the same game and it is proceeding normally; I guess maybe this should be marked closed.
Sorry, this is a duplicate of 32852, didn't think it posted the first time then couldn't figure out how to delete duplicate
I am having the same issue, going through iron swords like crazy. I don't know whether this is related, but several times after I have lost something a slot is filled by a duplicate of what I had in another slot; so, I might lose a sword but find 2 slots with 20 bones when I only had 20 total before.
It happened again. I think it has something to do with holding tools in hand, or switching between them. The first time it happened I was using a pickaxe to shave down a hill - suddenly I couldn't move at a pace above a slow crawl and doors and chests would not open if anything was held in hand. While playing with a backup copy the same thing happened (slowed down, can't open doors) when I was using a bow and arrow.