This problem is related to the favorites shortcuts disappearing, this has been a known problem for some time and is related to the corruption of the Outlook.xml file. There currently is no solid fix yet but some have luck in rebuilding the Outlook.xml file but this will need to be done again when the file corrupts again.

See how to rebuild it here: http://blog.palehorse.net/2007/09/26...ite-shortcuts/

See on of the very long ongoing threads about the issue here: http://social.technet.microsoft.com/...2-c27ea9a182de