Rick, this reminds me of a bug report inserted to dev.tw.o, that Ithink it hasn't been addesed so far.
It also happens to me, using Catalan Firefox browser, when I'm not logged in to tw.o, and I visit de.tw.o, I see no homepage (siki page).
I guess it's something related to bestlanguage feature, that they haven't defined any page with your default lang (browser), and there is no page to show.
But that's only a guess...
I'd suggest to open a new bug report at dev.tw.o.