We have a strange issue where every time we try to enable a trunk on our VSS switches, we lose our EIGRP adjacencies.  We have an 8-port 10GE blade in slot 9, and we are using ports 1/5/4, 2/5/4, 1/9/8 and 2/9/8 for our links between the 2 chassis.  We deployed 2 new 6120 fabric interconnects for our UCS project.  When I try to enable port 1/9/1, I lose my EIGRP adjacencies to my 2 core switches.  On 1/5/5, I have a link through a 4270 IPS going to core1, using a /30 on vlan X.  On 2/5/5, I have a similar setup going to core2.  Obviously losing all connectivity to my server farm is bad, so I can't leave the link on to troubleshoot.  Any ideas as to what might be causing this?  I have tried it in the past, and that's how we ended up with the routed server farm block.  I wanted to trunk the vlans to the server VSS switch, but it kept dropping EIGRP adjacencies.  Ports on blades 1 or 2 in the VSS work fine as trunks, and ports in blade 9 work as access.  I attached a crappy network diagram.  Thanks.