Some of our SharePoint Index servers are showing the following event
in the server event log and as a result, incremental crawl did not run.
This event appears to be intermittent and unpredictable. I searched MS
site and internet and could not find much info about it. Has anyone seen
this event and know what causes it and how to fix it? THANKS!

SOURCE: Office Server Search

Category: Gatherer

Type: Warning

Event ID: 2423

The update cannot be started because all of the content sources were
excluded by crawl rules, or removed from the index configuration.

Context: Application 'SharedServices1', Catalog 'Portal_Content'

Details:

Unspecified error

(0x80004005)

For more information, see Help and Support Center at
http://go.microsoft.com/fwlink/events.asp.

You have several options:

First, simply specify a different WSS Search database in Central
Administration, then start  the service from Central Admin, Operations,
Services on Server

Second, you could load SQL Express Mgmt Studio on another machine,
connect to your SQL EE server, and remove the WSS_Search_DEVSHAREPOINT02
database.

The lazy way might also work ;-) - you can reset a WSS search
database/index by using 'Stsadm.exe -o spsearchdiacriticsensitive
-setstatus True -force'.