Firefox hangs as in "not responding" or after a delay there is an unresponsive script warning?

Have the customer try disabling the protected mode feature of the Flash player plugin. That feature has security benefits -- it spins out various Flash processes to external threads with a lower ability to modify the system -- but seems to have serious compatibility issues on some systems.

You can disable it using the Add-ons page. Either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Plugins. On the right side, find "Shockwave Flash" and click the More link. Then uncheck the box for "Enable Adobe Flash protected mode" and try that for a day to see whether it helps.

Note on the above, since your question says it was posted with Windows XP: Flash doesn't use protected mode on XP, only newer versions of Windows.

It was posted from an XP machine but the machine with the problem is a Windows 7 machine. That was listed at the bottom of the question. Sometimes it was get an unresponsive script warning when firefox was first opened up. After you clicked to close the script the page would finally let you click on something. But when you would click the "+" to open a new tab, you do not get the unresponsive script error but the page just hangs and might take a couple minutes before you can click on anything in firefox. But when you set Shockwave Flash to "never activate" Firefox runs normal.

Came back onsite and unchecking "Enable Adobe Flash protected mode" does nothing. It still hangs up.

I should have suggested exiting and restarting Firefox after making that change, but perhaps that won't help either.

There seems to be an problem with the recent update(s) of Flash 22 on some 64-bit Windows systems. It's hard to know what to recommend.

(1) Adobe has a "extended support release" of Flash 18 that still gets security patches (about 60% of the way down this page: https://www.adobe.com/products/flashp.../distribution3.html). This presumably is more stable and probably compatible with most sites.

(2) If the customer never uses any plugins other than Flash and Silverlight (no Java, for example), they could use the 64-bit build of Firefox for Windows. Various users have reported that Flash works better in that build. It's available from this page: https://www.mozilla.org/firefox/all/

wicket82 said

But when you would click the "+" to open a new tab, you do not get the unresponsive script error but the page just hangs and might take a couple minutes before you can click on anything in firefox. But when you set Shockwave Flash to "never activate" Firefox runs normal.

The default new tab page with tiles of pages from history? Hmm...

By default, Firefox prepares 15 tiles for the new tab page. If Firefox was not able to capture a thumbnail image for a site in a history tile, it may try to do so in the background when you open the new tab page, and perhaps that is causing the hang.

To remove that from the page, I can think of two possible approaches:

(1) Remove it from History. You can launch your history in the Library dialog using either:

• Ctrl+Shift+h
• History menu > Show All History

Of course, this assumes you know what page it is.

(2) If that doesn't work, you could try to clear suspicious tiles from the new tab page -- with Flash disabled, of course.

Use Ctrl- to zoom out so you can see all 15 tiles, then hover suspicious thumbnails and click the "x" button at the upper right corner to block them from appearing on the page.

Does that help?