If Firefox is freezing or it will not show the bookmarks or almost any other problem with it, then Resetting or Refreshing it will fix it.
Older versions of Firefox with the orange button call it Resetting, and the newer version calls it Refreshing.
If you have an Orange Firefox menu button in the top left corner click on it > select Help> Troubleshooting Information.
Otherwise press the ALT key to reveal the menu at the top of the page.
Then Click on Help> Troubleshooting Information.
To continue, click Reset/Refresh Firefox in the confirmation window that opens.
It will restart Firefox.
What It Does Not Do
It does not remove:
Browsing History, Form History, saved passwords, or Bookmarks.
What It Does Do
Resetting Firefox will create a new profile folder. Your profile contains settings for plug-ins and home pages etc. The new profile will take a copy of your old settings. Your folder is usually stored here %APPDATA%\Mozilla\Firefox\Profiles\