Thanks for the response.
Yes, separatly they work great so I will just use them to unit test code on I guess. I think some how the answer is in these posts I found.
This guy provides a documented reason why we see this issue with the 5100 chipset:
http://john.crouchley.com/blog/archives/662
Here is another interesting workaround:
http://playground.arduino.cc/Main/EthernetShieldSDHardwareSPIMod
Best Regards.