Recently, I came across a new computer with a fresh installation of Mozilla Firefox that would prompt the user each time it was opened whether to make it the default browser.

After some research, it was determined that the problem was caused by corruption of the prefs.js file.

According to the Mozilla Knowledgebase, renaming this file solves such problems, and in fact, it solved our problem quite nicely.

If you run into a Mozilla Firefox issue where you answer a question "Yes" or "No" and the preferences are not saved, this may be the cause, as well as the solution.

Have a happy Memorial Day weekend, and safe browsing!