SYMPTOMS
Sub domain is set up as a sub folder in a domain. FrontPage is enabled on the sub domain. Then you enable FrontPage on the domain. Plesk shows that FP is enabled but it’s not working. You can check through Microsoft SharePoint Administration.CAUSE
This behavior can occur if one virtual server is nested inside another virtual server, meaning that the content folders for the virtual servers overlap. While this may be a valid setup for your Web server, the FrontPage Server Extensions cannot work properly in this environment.http://support.microsoft.com/kb/201522
Plesk 7.6.1 does not take this fact into account.
RESOLUTION
This problem has been solved in Plesk version 8.1.1. Consider upgrading Plesk to the latest version