The idea of fenses is to hold my icons where I want them...
Not have them go leaping out of their fences to exist, squashed into the small amount of 'unfenced' terroritory left on my screen! I have no clue what happened, there was no crash or diagnostics that I can see, and I just spent half an hour getting them back into the kinda-right places, with a very rough order -- alphabetical order would work better!
Any ideas WTF happened and how to avoid it in the future?