If you disable HWA in Firefox, does it also happen?
That's actually seemed to have worked, at least in getting Firefox up and running as it was yesterday (if not slightly better). Thanks!
Also I would delete the browser data which I'm guessing the uninstaller doesn't remove. Might be corrupted.
When removing Firefox delete the Firefox folder in: C:\Users\USERNAME\AppData\Local\Mozilla\Firefox
For ease of efficiency I've just restored a back up of my old profile that I had, but I appreciate that they may just reintroduce any corruption that was there. I've tried looking for the webpage I found on it before, but do you know what specific files contain the browser history and bookmarks? (Those are what I'm most interested in preserving, given that I've been using the same browser for probably the past five years.)
I'll call the tech guys about the system restore problem tomorrow. As long as the computer's stable and can do some graphic design work over the next week then I'm happy to ask them to look at it later on.