Windows-XP SP3 Security Center does not detect Endpoint Protection 11

Hi Guys,

I'm a network tech who just set up a 802.1x network with antivirus check on WIN7/XP clients.

All clients have SEP 11.0 installed, with Windows7 all is working fine but with XP sometimes the Security Center cannot detect the antivirus and I cannot authenticate to the network.

Do you know if there is a procedure to solve this issue?

Thanks for your assistance.

Dario