Xserve activity lights

We have a cluster of 10 xserves here, and some of them will give us what seems to be a code with the system activity lights on the front. The activity lights that typically show cpu activity no longer activity show processing going on, but instead will have every other light stuck on. So, lights 1, 3, 5, and 7 on the top and bottom rows will be lit up permanently. Reboots, zapping pram, etc... won't resolve it. If a machine in the cluster crashed sometimes it will come up with the odd activity lights as well. What is more interesting is that when this happens if you boot to another OS (i.e. my firewire drive or the install DVD) the lights will function properly. Then, reimaging fixed 2 of the serves that had the issue, while causing it to happen on another 2. These are all quad-core intel xserves running Leopard 10.5.4, 4 GB Ram, base configuration without any services running. They are actually being used in a cluster for episode engine. Thanks for any input you have, Jason