They should have the same subscription status. Are they all activated with the same LiveID? What version of OneCare are they on? Is one PC a hub, and can it see the other PCs in the Circle?
Are the two expired PCs set with the correct date/time? In OneCare on the two expired trial copies, under Help/About in OneCare do they show the subscription ID or trial?
Did you remove these 2 PCs from the OneCare circle from a hub PC?
-steve