Using stsadm to stop the osearch service will blat all the indexes:
In command prompt try running:
taskkill.exe /F /IM mssearch.exe /T
– this will terminate all mssearch.exe processes and their dependencies and then restart the mssearch.exe service again ( this might take a couple of minutes – you can check in Task manager when the service is up again).
If the above does not resolve the issue, then reboot the index server