I created such a snarl, tangle knot in my ball of wool that I had to cut it and rewind it into two balls and start again. In the effort of being a supremely thrifty knitter I decided that if I wound a ball of wool, used both ends, started 2 socks at the same time that I would be able to knit til the wool ran out thus preventing the dreaded leftover stash (which just goes to Rochelle anyways). So.....all was well through the toe, foot and heel. Somewhere up the leg a loop came out of the centre of the ball. I stuffed the loop back in, the loop came out agai, I re-stuffed. Then the loop came out and wound itself around everything, grew tentacles, and well became unmanageable.
I weighed the remaining ball, 34 grams left. So I cut the yarn from the project, untangled the mess and re-wound the first ball. It came out to 18 grams. I wound the second ball and magically it was 20 grams and now the first ball weighed 16 grams.
In the end the sock will be done but I don't think that I will ever try this again.