by Ron Grzywacz (http://forums.microsoft.com/technet/showpost.aspx?postid=1130848&siteid=…)
Ensure your permissions are set as noted below. Then try to restart the service from central admin.
Fixing Search Propagation share issues
http://technet2.microsoft.com/Office/en-us/library/9b1d6136-a05f-41f9-86…
In the Query Server Index File Location section, select one the following:
• Configure share automatically
Select this option to automatically configure the share on which you want to store the propagated index. Type [...]