LACP EtherChannel

I am trying to configure LACP between our Cisco 3750 stack and an EMC ns-120.

I have 2 GigabitEthernet ports that I have put into port-channel 20, please see the below config for the 2 interfaces¿

interface GigabitEthernet2/0/10
description EMC
switchport trunk encapsulation dot1q
switchport trunk native vlan 101
switchport mode trunk
speed 1000
duplex full
channel-protocol lacp
channel-group 20 mode active
!
interface GigabitEthernet2/0/12
description EMC
switchport trunk encapsulation dot1q
switchport trunk native vlan 101
switchport mode trunk
speed 1000
duplex full
channel-protocol lacp
channel-group 20 mode active

When using the above configuration the links do not come up, the port-channel interface and 2 physical interfaces show as notconnect.

However, when I switch the mode to 'on' (therfore not use a protocol) the etherchannel comes up no problem.

I have been assured that the EMC SAN is configured correctly and is able to use LACP.
I have also tried 'passive' mode with no joy!

Any help is greatly appreciated.
Pete