This is something I came accross a couple of months ago when I was trying to access SharePoint search through code - it gave the error "Your search cannot be completed because this site is not assigned to an indexer. Contact your administrator for more information." Apparently, there was something wrong in the configuration, to solve this - do the following:
- Go to SharePoint Central Administration > Application Management > Content Databases (Underneath SharePoint Web Application Management).
- Select the correct SharePoint web application – click on the name of the Content databases - this will open the “Manage Content Database Settings” page.
- Make sure that the Search Server is set on the “Manage Content Database Settings” page.