Firefox 18 on Mountain Lion frequently hangs with spinning ball for 1 min while a page is loading, or while opening a new tab. No tabs useable

Question

Firefox 18 on Mountain Lion. Frequently hangs for minutes with spinning ball, usually while a page is loading (status bar says "loading..." "waiting..."), but sometimes just while on the same page. Other tabs and windows are not useable, even though only one tab is waiting. I usually have 2-4 windows open with several tabs each. Behavior is no different in safe mode. This is making the browser unusable.
In the past this happened and I've reinstalled or created a new clean profile, but it always recurs.

Answer 1

The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information.
Note: ''This will cause you to lose any Extensions, Open websites, and some Preferences.''
To Reset Firefox do the following:
#Go to Firefox > Help > Troubleshooting Information.
#Click the "Reset Firefox" button.
#Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
#Firefox will open with all factory defaults applied.
Further information can be found in the [[Reset Firefox – easily fix most problems]] article.
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