Do you have backup of recovery_timestamp.zip files? If yes, try to import them in the SEPM.
OR
If the SEPM IP and hostname remains same & If the client-server communications breaks, you can quickly restore communications by replacing the Sylink.xml file on the client computer. You can replace the sylink.xml file by redeploying a client installation package. Use this method for a large number of computers, for the computers that you cannot physically access easily, or the computers that require administrative access.
http://www.symantec.com/docs/HOWTO81109