A lot of cursing, but as always Google to the rescue, Shockwave Flash Plugin was the devil causing the problem. Just disable it and voila, back to normal. Solution found here www.computing.net/…/firefox-page-blanks-out-after-loading/..
@Update: Did just help for a while, so I enabled it and it all worked just fine. So now waiting until the next time when I have to disable it. And by the way, I do have the same problem on my laptop running Ubuntu as I have on the laptop I use at work running Windows XP.