Firefox - fonts not displaying correctly - screenshots included

Hi all, hoping for some help please...

Windows 7 64bit Enterprise with latest version of Firefox:

My fonts on various websites aren't displaying correctly in Firefox on my new work laptop (new build so I'm adding my apps from scratch). I've used M&S money as an example - it happens on other websites as well though.

Here's how my new laptop is displaying the links on the main page:



...and here's how they should be displayed (screenshot taken from old laptop)



The culprit font appears to be Arial Black - it's displaying that instead of what looks like just Arial but bold.

I've Googled it, loads of suggestions like delete your profile, re-install Firefox, try resetting your fonts etc; tried all of them to no avail, but I do think it's a Firefox issue as the links display ok in Chrome & IE.

Something I tried which I can't unerstand is that I installed FF Version 3 (found an old installer file) and that displayed the links exactly how they should be, so it appears to be the later versions?

Any help appreciated, it's driving me mad

thanks for the suggestions netbox, regarding the hw acceleration that is currently checked, when i uncheck it it doesn't fix the problem, but it does something i've not seen before when unchecking it - it makes all of my other text including the address bar & tab titles look like it's lost it's "clear type" finish. odd, not seen it do that before...



regarding the about:config options, both of those are set to false as per your screenshot.

thanks for the suggestions, don't suppose you've got any more?

thanks...