Make sure that you click the link properly.

You can disable auto-scrolling to prevent that from happening.

• Tools > Options > Advanced > General: Browsing: "Use autoscrolling"

Just tried that. It didn't make a difference, I still have the same problem with both links and closing tabs.

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.com/kb/Safe+Mode

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

If it does work in Safe-mode then disable all extensions and then try to find which is causing it by enabling one at a time until the problem reappears.

• Use "Disable all add-ons" on the Safe mode start window to disable all extensions.
• Close and restart Firefox after each change via "File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit")

In Firefox 4 you can use one of these to start in Safe mode:

• Help > Restart with Add-ons Disabled
• Hold down the Shift key while double clicking the Firefox desktop shortcut (Windows)

I'm now in Firefox Safe Mode, and there is no change to the problem.

You can check the settings in Control Panel > Mouse and make sure that the middle mouse button is set to default

I shut my computer down, and the next it's suddenly working ok, so it might have been something else related to my computer.

The problem reappears when I have Adobe Photoshop or Acrobat open at the same time.