So as of the last batch of updates I applied to my laptop (running Fedora 21), Firefox started acting really weirdly. In particular, I was seeing the following things:
I did a lot of searching around. I came across some older posts on support.mozilla.org, but none of the suggestions there were helping (and most of them were discouraged by Mozilla folks anyway).
After a lot more searching, I found Debian bug #775645.
It described many of the issues I was having and a few more. Bingo!
It mentions that something set the
dom.indexeddb.enabled preference to
false and that setting it back to true reverted all functionality back to normal. And so it did.
I'm writing this post in the hope that anyone who uses Firefox and runs into a similar issue finds it useful. I'm not sure which plugin specifically set
dom.indexeddb.enabled to false -- it wasn't anything I set manually.
Hopefully this is helpful to someone.