setlang= not working on live site

[Tyblitz]

Just uploaded and migrated a site developed on localhost to a new hosting provider but am experiencing problems with setlang. Have installed I18NBase and I18N but keep getting the following message from provider.

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, support@iomart.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Hey cobber, what server are you on? If it's Apache 2.3 or 2.4 and mod_access_compat is not enabled, this might be a problem with incompatible plugin .htaccess files. If you can access the httpd.conf file, you can check it there.
If you have access to Apache error logs (from your host panel), check them (search for "500"), and report error message here.
If you're on a shared host, create a file phpinfo.php with just this code: <?php phpinfo(); ?> and upload it to your GS root path, then load it in the browser, and Ctrl + F search "apache2handler". Check the version, and whether you can see mod_access, or mod_access_compat in the 'Loaded Modules' row.