To rule out Flash as the culprit, could you make a couple of changes to help minimize Flash issues? These are: set Flash to Click-to-Play ("Ask to Activate") to delay Flash from starting on a page until you approve it; and disabling the protected mode feature of the plugin.

(1) To set "Ask to Activate", open the Add-ons page using either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Plugins. Look for "Shockwave Flash" and change "Always Activate" to "Ask to Activate".

When you visit a site that wants to use the Flash, you should see a notification icon in the address bar and one of the following: a link in a black rectangle in the page or an infobar sliding down between the toolbar area and the page.

If you don't see an immediate need to use Flash, just ignore the notification.

(2) There is a hidden setting to disable the protected mode feature of the Flash player plugin, which works around incompatibilities with some systems. I suggest trying this for a day to see whether it helps:

(A) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(B) In the search box above the list, type or paste flash and pause while the list is filtered

(C) Double-click the dom.ipc.plugins.flash.disable-protected-mode preference to switch its value from false to true.

This might not take effect until all Flash has been unloaded for a few minutes, or you close Firefox.

Thanks for the response jscher2000, but unfortunately this hasn't solved the problem!

I'm having a hard time thinking of what Firefox would want to do at 10 minute intervals... Does it matter what pages are open at the time?

It doesn't matter what windows are open, but I'm beginning to think it's the laptop itself, not Firefox. I think I've just noticed it on Firefox because I use it more than other programs.