Firefox question

I hope this makes sense so someone can help me.

Sometimes, my Firefox flips back to a previous version and I cannot get the current version back until something miraculously happens and it desides to flip back. It may be weeks before this happens. Make sense? When the older version is running, if I try to upgrade it and it won't. I can't use current themes and extentions when in that version. Also when I'm in the old version, I can't for the life of me get back to the current version.

I was just running the old version for a couple of months, it just recently flipped back to the new and improved version, lol. The booksmarks from the old version are trapped somewere in cyberspace and I'd like to get to them to add them to the current version.

Also, I'd like to get rid of this problem for once and for all. If anyone can make sense out of this post and help, I'd surely appreciate it.