NIS 2012 not updating automatically in laptop battery mode

Hi

No problems getting the virus definition updates when my notebook is connected to mains power but when the notebook is running off battery, Norton does NOT update automatically...i have to click the liveupdate link to get updates. Powersaving mode is set to "off", "automatic liveupdate", "pulse updates", & "smart definitions" are all enabled. Any idea what's wrong?

Cheers