Firefox crashes on attempts to access windows user profiles (maybe)
After several reinstalls and other attempts based on comments found in various solutions posts, I am still stuck here. Firefox installs and runs ok with elevated permissions (run as administrator), but crashes frequently when run normally. In normal mode it always crashes when opening the "options dialog" about:preferences page and when downloading a file. It crashes sometimes when browsing. Installing in non-elevated mode gets to about 90% and hangs, installing elevated works fine. One explanation would be that firefox does not have access to C:\users\<profile>\... at the level it needs, but I have not been able to find out why. IE seems to work fine, and I have reset to the default security settings in IE. The crash signature say nothing useful about the reason. I have adjusted all firewalls up and down the scale. Everything worked until I had some other problems that required some aggressive upgrades, and now everything but firefox works. Basic browsing in firefox is ok, and plugins like flash and acrobat are working. So I have been stuck on this for about a week, limping along and trying things. I don't know if it is firefox specific or something systemic, but it would be nice to know what the problem is so I have some clue how to fix it. Any ideas would be really appreciated. Thanks.
Chosen solution
So my next move was to create a new user account. The new user was able to use Firefox normally. Several other issues existed with the original user account, but none as bad as Firefox. Anyway, with a new user account created and the old one deleted, it appears things are finally normal again. My guess is that some element deep in the account data was deleted, by something or someone, and Firefox needed to access it but did not check for the possibility that it was not there.
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Hello! Try these steps to ensure you are correctly uninstalling Firefox.
Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove Firefox program files and then reinstall Firefox. Please follow these steps:
Note: You might want to print these steps or view them in another browser.
- Download the latest Desktop version of Firefox from mozilla.org (or choose the download for your operating system and language from this page) and save the setup file to your computer.
- After the download finishes, close all Firefox windows (or open the Firefox menu
and click the close button 
).
- Delete the Firefox installation folder, which is located in one of these locations, by default:
- Windows:
- C:\Program Files\Mozilla Firefox
- C:\Program Files (x86)\Mozilla Firefox
- Mac: Delete Firefox from the Applications folder.
- Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
- Windows:
- Now, go ahead and reinstall Firefox:
- Double-click the downloaded installation file and go through the steps of the installation wizard.
- Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.
More information about reinstalling Firefox can be found here.
WARNING: Do not use a third party uninstaller as part of this process. Doing so could permanently delete your Firefox profile data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. These cannot be easily recovered unless they have been backed up to an external device! See Back up and restore information in Firefox profiles.
Please report back to say if this helped you!
Thank you.
I did go through this procedure again, even though it would probably be the 6th time. This time was slightly different since I downloaded and ran the stub rather than the specific installer. The result was that this time the installer did work without complaints or hangs. However, firefox still hangs on opening about:preferences I assume the problem remains the same.
Chosen Solution
So my next move was to create a new user account. The new user was able to use Firefox normally. Several other issues existed with the original user account, but none as bad as Firefox. Anyway, with a new user account created and the old one deleted, it appears things are finally normal again. My guess is that some element deep in the account data was deleted, by something or someone, and Firefox needed to access it but did not check for the possibility that it was not there.