tmarts said

. . . . and every program loaded blotting out numbers in accounting programs and words in WP programs.

Nothing about Firefox should do anything in other programs, or are you accessing those files using Firefox?

Start Firefox in Safe Mode {web link}

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• Anti-Rootkit Utility - TDSSKiller (for more info, see this alternate TDSSKiller download page)
• AdwCleaner (for more info, see this alternate AdwCleaner download page)
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista if you don't already have one. Windows 8/10 have antivirus protection built-in.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

Did this fix your problems? Please report back to us!

Not accessing any programs in Firefox.

Have you tried simply restarting your computer? The little Firefox icon kind of looks like it's just a visual glitch from the Windows Start Menu. Restarting your computer should fix that.

Yes. As I posted in the question, the icons disappear when I restart the computer. Your analysis seems on the money. Also, I ran a 2-hour scan with MSERT. Nothing was detected. Thanks!

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems