http://www.google.com is one of the few useful test sites -- what language does that come up in for you?

Comes up in English. Always have.

Now, I'm using FireFox (the latest Mozilla release), and for the 'enabled' languages, I have English (US) ["en-us"], English ["en"], and Japanese ["ja"], in that order. Same thing for IE. While Japanes is in there, it's NOT at the top of the list (so therefore, shoudn't be listed first.. In theory.) I have JA listed mostly because, yeah, I do do alot of surfing on Japanese sites, and notice that that helps in displaying the correct character set..

Me.