IRB and channel groups help needed

[pfisterfarm]

I've got a 8540 switch running 12.1(20)E set up with IRB and I've got
two interfaces I'm looking at:

interface GigabitEthernet0/0/3
no ip address
no ip redirects
!
interface GigabitEthernet0/0/3.1
description Native VLAN
encapsulation dot1Q 1 native
no ip redirects
!
interface GigabitEthernet0/0/3.99
encapsulation dot1Q 99
no ip redirects
no cdp enable
bridge-group 99

The other interface is Gigabit0/0/4 and is set up the exact same way.
I'd like to be able to set up a channel group for those two
interfaces. I set up the port channel like:

interface Port-channel1
no ip address
hold-queue 300 in
!
interface Port-channel1.1
encapsulation dot1Q 1 native
no ip redirects
!
interface Port-channel1.99
encapsulation dot1Q 99
no ip redirects
bridge-group 99

But if I apply it to one of the interfaces, I get an error: "Error:
Interface has sub-interface configured". I can take the subinterfaces
off temporarily and set up the channel-group, but it I try and re-add
the subinterfaces, I can't do that. Is this something that is
possible? If so, what am I missing?

[bod43]

I would have thought that you configured the sub-interfaces on the
port channel only. Not the physical interfaces.

By the way as I am sure you
know there are two very distinct 8500 models, one
very ATM-y and one Ethernet-y and you need to be
careful which documentation you look at. CSR? Was
decades ago:)

Have a look at this.

http://www.cisco.com/en/US/products/hw/switches/ps628/products_configuration_example09186a00800ef797.shtml
"Configuring EtherChannel and 802.1Q Trunking Between
Catalyst L2 Fixed Configuration Switches and a
Router (InterVLAN Routing)"

Hope it might help.