Here are the steps to fix this problem:

Step 1:
Right click on My Computer and Goto Computer management…
Select Services and applications
Start indexing service If not started.

Step 2:
* Central Admin > Application Management > Office SharePoint Server Shared Services > Create or Configure this farm’s shared services
* Shared Services Provider (drop down) > Edit Properties
* Edit Shared Services Provider > Index Server: Verify the index server is set

Step 3:

Single Server Farm

On the MOSS 2007 server:
* Start > Run > CMD > stsadm.exe -o osearch -action stop
* Start > Run > CMD > stsadm.exe -o osearch -action start -role queryindex

Multiple Server Farm

On the MOSS 2007 Front End Web/Query server:
* Start > Run > CMD > stsadm.exe -o osearch -action stop

On the MOSS 2007 Index server:
* Start > Run > CMD > stsadm.exe -o osearch -action stop

On the MOSS 2007 Index server:
* Start > Run > CMD > stsadm.exe -o osearch -action start -role index

On the MOSS 2007 Front End Web/Query server:
* Start > Run > CMD > stsadm.exe -o osearch -action start -role query

Step 4:
* Goto Central Admin ->Operations ->Topologies and services ->Services on server
* Click “Office SharePoint Server Search”
* Make sure the user has sufficient permission to access database.

Note: If your Search query and indexing server are same then set Both options “Use this server for indexing content” and “Use this server for serving search queries” true.

Hope, It helps.