Hi sreec. Thanks for the information. I was told that the XenDesktop connection manager wouldn't add the VMs to the desktop pools. There was a red x listed next to them. That's all of the information I was given. These VMs were the same ones in the pool before the vCenter upgrade to 5.1. My co-worker said he rolled back the vCenter upgrade and the VMs worked fine. I asked if the hardware\tools was upgraded as well and they weren't sure.
I'm going to set up a vSphere lab and with 5.0 and test the upgrade with XenApp\Desktop. I'll have to do some reading regarding the upgrade when vCloud and VSM are involved.
Thanks again for the info!