Maybe something changed in the program shortcut you use to start Firefox. Can you check right-click > Properties > Compatbility tab and make sure nothing is selected there?

I've never tried this myself, but the forum has a standard set of steps for a "clean reinstall" of Firefox to replace damaged program files. During this process, you are not removing personal settings, but you are removing some shared add-on folders, which would affect Windows Media Player and perhaps other plugins/extensions installed that way.

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.

1. Download the latest Desktop version of Firefox from http://www.mozilla.org and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu).
3. Delete (or if you're nervous, move or rename) the Firefox program folder, which is located in one of these locations, by default:
   • Windows:
     • C:\Program Files\Mozilla Firefox (32-bit)
     • C:\Program Files (x86)\Mozilla Firefox (64-bit)
   • 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.
4. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

Does that help?

Did you check for problems with the temp folder (%tmp%, %temp%)?

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) as a test to see if that helps.

I am also having permission problems.

I am on ubuntu 13.10 64bit.

The directory permissions (/stuff) are wide open:

drwxrwxrwx 10 sforeman sforeman 4096 Dec 6 11:52 stuff/

I did this on that directory: sudo chmod 777 stuff

no dice

If I go into that directory via terminal I can add a directory/file. If I try to set my save directory to a new directory in there (/stuff/asdf) I get permission denied when I try to create the folder within firefox.

What is weird is I can save files into my home directory and into the /tmp directory. It feels like something in firefox has been hardwired to prevent any changes outside of those 2 directories.

I wiped firefox via apt-get purge and removed the settings directory in my home directory and reinstalled it. The issue persists.

I had to give up and created a directory in my home directory and symlinked to it from where I wanted it. It was the only thing I could do.

When you change the download folder can be downloaded file. I get the message: The file could not be saved because you do not have proper permissions Choose another save directory. Can be downloaded only in C partition (default download folder) and I can not change save directory

Hi tatomir, when did this problem start for you?

By default, on Windows, Firefox will download files to your system temp folder and then move them to the designated destination. Of course, that only applies to the drive that contains the system temp folder... You are having problems saving directly to a different drive?

Does this affect all kinds of saves? (e.g., Save Page As, Save Image As, download, etc.)