Problem with workbench session

Hi,

I am getting the following error when I am working on the workbench.
"Your session authentication has expired and needs to be renewed". When I see the Livecycle ES logs, I am seeing following message -

IDPLoggedExce W com.adobe.idp.common.errors.Logger$LogConsumer run UserM:GENERIC_WARNING: [Thread Hashcode: 1460688656] | [AuthenticationManagerBean] errorCode:12804 errorCodeHEX:0x3204 message:Could not validate SAML Token --- Assertion is not valid. Current time is greater than NOTonOrAfter time specified in the Assertion

Any idea why this could happen? I did a server based operation (a template save) just a few seconds before I got this error.

Thanks,
Badri.