I have faced an interesting bug on a customer's site.
We were trying to configure the user profile import feature of MOSS 2007. We used the default configuration since the MOSS 2007 server was a member of the domain. We were getting a warning ( god, I can't remember the warning detail, so I can not write it here, stupid me :/ ) that says, it can not connect to the domain controller ( it was something like "access denied" and "object not found" or stuff like that ).
The solution to the problem is so hard to find. Let's say we have a domain like "nezihtinas.local". MOSS 2007 defines the domain as "NEZIHTINAS.LOCAL". When the import stars, it converts the domain name to lowercase, and you expect it to be "nezihtinas.local"; but you're wrong :P. The lowercase conversion depends on the regional setting of the MOSS 2007 server. Since our server's regional setting was "Turkish", the domain name is used something like "nezŸhtŸnas.local", so MOSS 2007 can not find the domain controller and it gives a warning.
We changed the regional setting of the MOSS 2007 server to "English" and the problem was solved. There are many bugs in the product but this one was tough though :P.