Just looking for a bit of clarification on this. From what I've read, on the 3750s jumbo frames are enabled globally using the "system mtu jumbo" command. It also looks like you can specify the mtu size of specific vlans. So if you were looking to enable jumbo frames for one vlan would you set the size globally and then set the mtu for all other vlans to 1500?
I have this problem too.