There has been a breaking change the list of culture names in .NET 2.0. This change applies to Windows Vista and anyone who has installed patch ms07-049.
Shawn Steel has posted a mapping table between the old and new names and suggestions on working around this issue. More information can also be found in KB 939949.
The work around is basically to create a new culture with the old name that has the new name as its parent. The table posted by Shawn Steel suggests Microsoft has already does this for the two Chinese cultures. Why this wasn't done for the other cultures has not been explained.