.htaccess Error : Invalid command 'AuthGroupFile'
Assuming you're using apache 2.2, this means you're missing the mod_authz_groupfile module.
You need to look in your server config and look for the line that contains:
LoadModule authz_groupfile_module modules/mod_authz_groupfile.so
or something similar and make sure it's commented out.
Otherwise, just leave out the AuthGroupFile
directive, it doesn't look like you're using it anyways.