It looks like a problem with Flash. Are you using the latest Adobe Flash 11.3 that is known to have problems with Firefox whether or not RealPlayer is installed?

Take a look here: How do I troubleshoot Flash Player's protected mode for Firefox? Just scroll down to the section named below and start from there:

• Problem: RealPlayer is not installed, Flash Player crashes in Firefox

Make sure to also try the last resort option listed there!

If the above fails, you can always try to downgrade to Flash 10.2.

1. Download uninstaller: Flash uinstaller
2. Install Flash 10.3 from here: Flash 10.3

Hope this helps!

Try to clear the Flash local storage and settings.

• Windows Control Panel > Flash Player > Storage: Local Storage Settings **Remove a specific domain: Local Storage Settings by site **Remove all domains: Delete All and Delete Data

Flash Website Storage Settings panel:

• http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager07.html

Global Storage Settings Panel:

• http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager03.html

I notice the Flash installed is 32-bit and my PC is 64-bit. Any connection with the problem ?

No. Firefox is a 32 bit application, so you need a 32 bit Flash player version for Firefox.

It solved one problem (thanks) but created another. Many of the instructions on the Adobe page 'http://forums.adobe.com/thread/1018071' didn't appear to be for Windows 7 and I didn't have enough PC knowledge to find a way around them. Last resort - uninstalled Flash 11 and installed version 10.2. Problem solved. All YouTube clips work properly. The downside is that none of the Flash Videos stored in my RealPlayer Library work. The program is insisting on loading Flash 11.

They do work for Windows 7. Which part were you having problems with?

The only alternative I have for you short of re-installing Flash 11.3 just to go through the above-mentioned troubleshooting again, is to install Flash 11.2. However, I am not sure if this will recreate the problems in 11.3. My guess would be that it won't because the huge Flash problem with Firefox only came up with version 11.3. If it is important to see your Flash Videos stored in RealPlayer again, then go ahead. Besides, you can always downgrade back to 10.3 as mentioned above.

1. Download uninstaller: Uninstall Flash
2. Install Flash Player 11.2.202.235 from here: Archived Flash Players

Also, make sure to disable automatic updates for Flash when the prompt comes up. Select "Notify me of updates."

If you don't mind re-installing Flash 11.3 again, here is what I would do according to http://forums.adobe.com/thread/1018071.

1. Follow the troubleshooting steps starting from Problem: RealPlayer is not installed, Flash Player crashes in Firefox
2. Perform Last resort: Disable protected mode. If that doesn't work, a downgrade to 11.2 or 10.3 is needed.

I decided to use Chrome until the FireFox v Flash problem has been fixed.

Chrome comes with the latest Flash but neither YouTube or RealPlayer would work with it

So I installed the latest Flash myself. YouTube worked OK but Real Player insisted on loading Flash itself.

So Flash has now be loaded 3 times. Both YouTube and RealPlayer now work as they should.

Next I ran Firefox to test YouTube and RealPlayer. Both are now working correctly (even with the latest Flash installed).

Then as another test, I deleted Chrome and the old problem returned. So it appears that FireFox works with YouTube only when Chrome in installed on the PC, but RealPlayer still works anyway.

So the answer seems to be to install Chrome but not use it.