After downloading a newer version of firefox, the browswer only works in one user profile at a time in my windows
We have 5 user profiles in windows and the only profile where firefox works is the profile where it was downlooaded. If a download it on another profile, it will work there, bit no longer in the original profile.
Opaite Mbohovái (1)
When exiting Firefox, please exit with File > Exit or "Firefox" button > Exit, not with the "X" which just closes the window. You may still have to check if Firefox.exe finished by checking in the "Processes" tab of the Windows Task Manager, Use "Ctrl+Shift+Esc" in Windows 7 to get quickly to the the WTM.
You can only have one profile in use at a time, unless you use "-no-remote" on the profiles that are not your default profile. see
For a longer answer see https://support.mozilla.com/questions/846534 after reading the MozillaZine article.