Have you downloaded any add-ons? For example it took me a while to realise 'NoScript' was blocking some of my games. If not then although it may alter your browsing safety you could edit the security options. i.e. it could be classed as a pop-up and therefore is blocked by Firefox security.

I don't really know how to check where my add-ons are...I dont really know my way around my computer that well. haha I do understand what you're saying though...my boyfriend did check my add-ons last night but I don't think he would have thought of 'NoScript' being the cause of anything. I'll have him check it out when he gets home. thanks.

Facebook games are usually Flash based.
Your More system details list show that you have the Flash plugin, so that should be working.
Make sure that you do not block Flash.

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)

cor-el is probably correct with the old copy-n-paste ;)

but add-ons are checked easily by going to Firefox(top left)>Add-ons it should take you to a list of yours installed. If it doesn't then click on Extensions.