Do you by any chance have the statement "language en_IN" in your
vimrc? If you do, then it means that your system doesn't accept en_IN
as a valid locale.
On Unix-like systems, "locale -a | less" (typed at a shell prompt)
will show you all the locale names known by the system. On Windows,
the locale names have a different format: if you are running Vim on
Windows, try "language English_India.10646" instead.
Best regards,
Tony.