A few days back, i was unable to import user profiles, after our development server crashed and fortunately we restored it using the last known back-up of the Virtual machine. All of a sudden our user profiles import and search crawling and indexing services stopped abruptly, throwing a nasty "An indexer is not assigned to the Shared Services Provider 'SharedServices1' error.
Luckily i found a solution for the same:
a. Log in to Central Administration
b. Select your Shared Services provider and choose "Edit Properties" from the drop-down context menu
c. Configure your Index server and it works like a charm...
