Whidbey Beta 2 bug with CreateSpecificCulture() for Neutral Custom Cultures.
There's a bug in Whidbey Beta 2 where CreateSpecificCulture() will return invariant for any neutral custom culture, including both replacement and supplimentary cultures. So even replacements of something like "en" will have Invariant instead of "en-US" as their specific culture.
That's why we have betas :-)