Windows 7: Taskbar icons "flash," but don't open, among other things going wrong

This has happened several times over the past 3-4 months:

Surfing away on Firefox. Go to take a break and set computer on Sleep (Sleep is default when idle). When I get back, FF is not responding and clicking the taskbar icons brings on a whole array of responses such as:
1. Thumbnail of icon will flash above the icon, but won't open
2. Selecting an icon may open the intended program, but it is usually unresponsive.
3. The only way to get out of this mess is to manually shut down (on re-boot, all is functioning well)

I used to use Firefox several versions back. But the same issues you've described affected my computer. My "fix" was to uninstall Firefox and reinstall a fresh copy. The problems would disappear for a few weeks and then come back for no apparent reason that I could find. I got tired of dealing with the hassle and just stopped using Firefox.

You may find these Mozilla support articles helpful.

Troubleshoot and diagnose Firefox problems | Firefox Help

Uninstall Firefox from your computer | Firefox Help

Internet Explorer or Google Chrome is all you need.

I really hate to give FF up. I have tweaked it so that I can surf without hardly doing anything. I don't believe that IE9 comes close to FF in tweakability; and although I have never tried Chrome, I get the feeling that it also is not as tweakable as FF.

If you don't mind the inconvenience you probably don't have to give up Firefox. Try uninstalling/reinstalling a fresh copy and see if it corrects the problems. The Firefox uninstaller includes the option, "Remove my Firefox personal data and customizations". This option will remove your Firefox user profile data (bookmarks, passwords, cookies, extensions, preferences, etc.). DO NOT select this option if you want to keep your Firefox profile data and settings. Another Mozilla help article for your reading pleasure:

Uninstalling Firefox - MozillaZine Knowledge Base

I don't mind the FF fresh install, but I've also posted the question on FF Support forum to see what they have to say.

It will be interesting to see if they have a solution. If you and I have experienced the same issues there's got to be others out there.

Agreed.