Try Firefox Safe Mode to see if the problem goes away. Firefox Safe Mode is a troubleshooting mode that turns off some settings, disables most add-ons (extensions and themes).

If Firefox is open, you can restart in Firefox Safe Mode from the Help menu:

• In Firefox 29.0 and above, click the menu button , click Help and select Restart with Add-ons Disabled.
• In previous Firefox versions, click on the Firefox button at the top left of the Firefox window and click on Help (or click on Help in the Menu bar, if you don't have a Firefox button) then click on Restart with Add-ons Disabled.

If Firefox is not running, you can start Firefox in Safe Mode as follows:

• On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac: Hold the option key while starting Firefox.
• On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
  (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

When the Firefox Safe Mode window appears, select "Start in Safe Mode".

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one. Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to find the cause.

To exit Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help others with the same problem.

Hi, thanks for your reply. I actaully found something in the FAQ of YouTube Downloader that suggested changing settings in Internet Explorer (bizarre, as I never use explorer) and that seems to have done the trick. The information I followed was:

If you receive a "Pause, waiting for internet connection" or "Failed 6" error please perform the following actions: Regardless of your default web browser', reset your Internet Explorer settings by going to "Tools" (Alt + X keyboard shortcut) > "Internet Options" > "Advanced" tab. Select "Reset", making sure to choose the "Delete personal setting" check box.

I tried this and it seems to have fixed it - I can now copy and paste images, itunes can find song information and YTD is working again. Not sure how it works, but it did!

Thanks for your advice though, much appreciated.