DId you installt he ink aswell? If you havent you can download the ink from:
http://www.kaonet.net/page.php?id=75&a=dl
Uninstall the handwriting plugin first (plus>plugins>handwriting>uninstall [that could be for other versions though.) (also try removing the file MSNHandwriting.dll from your plug-ins directory, most likely C:\Program Files\Messenger Plus! 3\Plugins), then install the ink for ALL user, then run the handwriting installer, restart msn and you should see the tabs. I hope that helps you