Hi Lester,
Please try the following steps.
Check the connectivity of SEPM and the client...ping command
Check the policy serial number on the SEPM conssole as well as on the client side. If the policy serial number is the same that means there is no communication issue.
Create a new group and try moving the client to that group.
Try creating a new package and deploying it to the machine in question.
(http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2008042213451848)