I use Opera (take that Firefox users!) and have the same issue once a while, strangly enough it happens to all Guild Wars Guru tabs at the same time, and not individual pages.
Borkded here atm.. same white issue. I was gonna ask about/report it here, but then I found this thread. Never seen it before in the 2+years I've been reading guru forums. Weird stuff.
And I guess your css-files aren't doing what they're supposed to do ?
If you have a proper browser (not IE) you can disable css, for us normal people, we would like to have some non eye hurting colors!