I've cultivated a good number of addons while using Firefox. About a week ago, I noticed that youtube videos weren't automatically going to HD (which is an addon I have set up). I looked into it and when I went to my addons panel, most of them were gone, including my adblock. What's odd to me is that some ARE there. If all of my addons were gone, it would make sense that there's a problem there, but the fact that some have mysteriously vanished? I have no idea what to do.

I reinstalled the ones I remember I had, but I know I had quite a bit more that I'm still missing. I'm very upset because, as I said, I've cultivated these addons over a long time and I've found a very comfortable experience with all of them. Any advice? I have Sync installed but that doesn't help.