Firefox 220.127.116.11 was just released. This contains a bug fix (perhaps bug 265740, perhaps this security issue, perhaps something else) that gets rid of the crashes when using my Greasemonkey scripts, especially label colors and conversation previews. I have been running with all scripts enabled for the past couple of days and have not had any crashes. Hopefully the same is true for everyone else.
I have also updated the preview script with the latest Gmail IDs, in a similar manner that the macros script was updated.