Windows 2003 cluster fallback question

I have a Windows 2003 cluster with an Exchange virtual server running ok.  I have media sense enabled and failover works ok for all hardware failure scenarios.  My question is about fallback, lets say for example, that I unplug the ethernet cable on node1 in my cluster (the active node), and this causes the cluster to failover to the second node.  So far this all works fine as expected.  Now lets say I re-connect the ethernet cable on node1, and expect to see the cluster fail back over to node1.  This does NOT work as expected.  I have fallback set on the cluster to fallback immediately, but nothing happens.  Am I missing something?  Do I need to setup some other option or is there a trick to getting this to work?