I have moved your post to the- Encryption: EEM Managed forum for better attention (did not specifiy you used ePO)
Is that with HD encryption in progress, or fully encrypted?
Do you have EEPC SSO enabled?
What is PC OS?
This is when the drive is fully encrypted and yes we have EEPC SSO enabled. Should this be turned off?
I would try to turn it off, as a test.
There is possibility that in your setup, EEPC SSO cannot use cached Windows credentials and waits for network connection to display logon screen.