A US version of the recently releasedLoki v184.108.40.206 patch is now available from Dreamcatcher. Apparently the different patch is because Securom is used in the US but Starforce in Europe.
The patch addresses "Multi-Player bugs". More information.
Yeah - apparently the authentication is different as well - EU has CD-Key and DVD-in-drive whereas US has DVD-in-drive only … applying the EU patch to the US version meses things up to the point of needing an uninstall / reinstall. According to DreamCatcher, anyway.