Bladecenter switches acting funny

Today I had a nice problem. When a second switch was added to the a 3 com uplink switch the network went down. Not so very nice. I fixed it in a not so good way but it gives me a clue were to start looking for the error. I executed the following on both switches.

interface range GigabitEthernet0/17 - 20

spanning-tree portfast trunk

spanning-tree bpdufilter enable

spanning-tree bpduguard enable

!

Basically this means that the switch will not do Spanning tree on its external ports. Do not do this if you are unsure that you have loops or not. In my case I was quite sure so I just did it :) . Probably some 3 com spanning tree protocol that does not talk nice with rapid-pvst