We have a network with c6500 as distribution and c3750E stacks as access.
We use MST for failover/loop prevention.
I have seen a couple of times that when I connect a new 3750 and change spanning-tree mode to "mst" - the status of root port becomes "p2p (bound pvst)"
When the redundant uplink is connected we get a l2 loop. Seems like I have to boot the 3750 once after changing to "mst". After boot it gets correct status "p2p".
Any idea why?