Dropped network traffic over a bridge connection

Very strange and tough problem. I have a Cisco 6509 with one port connected to a remote location via 2 Cisco 1721 T1 WIC card routers configured as a bridge. Why bridge instead of route? Bridging allows VLANs to go over the wire and keep there VLAN characteristics (ID). I have three VLANs working over this wire now.  THe VLANs are configured as gateways on the 6509 (they have the dot one address of the subnet assigned to it.)
Details:
The 6509 port is configured as a VLAN trunk. The local router has a fast ethernet port and a serial port. THe bridge does nothing but forward traffic across the T1. On the other end of the T1 is just the opposite. A serial port passes the packets across to the ethernet port and then to the trunk port of a Cisco 3560 switch.
So, I go to setup another locations in EXACTLY the same manner over another T1. This time though it does not work. The local router is dropping packets.
More details. A packet capture shows the following:
I setup a PC on the remote end with a static address and ping the gateway which is back on the 6509. The ARP packets cross the bridge and hit the gateway which sends the ARP reply back to the originator. However, when the packet gets to the fast ethernet interface of the local router it drops it and will not forward it back across the T1 to the remote router or machine that requested the ARP.
What I have done:
I swapped the 2 1721 routers with different ones configured exactly the same way with no change.
I swapped the 1721 routers with each other and get the same results so the routers are essentially OK.
I took a patch cable and changed the wiring so that the TX was wired straight to the RX and vice versa. THis will simulate a T1 line. (I also made the line clock internal in this situation.) Same results, traffic is being dropped at the local fast ethernet interface on the return trip.
Like I said, this exact configuration, equipment and software works in another location.
I know this is an advanced problem and very complicated but I have run out of ideas. I have no one else to look at this. Any thoughts are welcome. Code snippets attached of the Trunk ports and the routers.

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Cisco 6509 trunk port
 
interface GigabitEthernet4/33
 description ***** Museum-T1 Circuit #11.DHXS.000826 *****
 switchport
 switchport trunk encapsulation dot1q
 switchport mode trunk
 no ip address
end
 
 
Cisco 1721 router
 
ip subnet-zero
no ip routing
!
!
no ip domain lookup
!
!
interface Loopback0
 ip address 10.6.1.249 255.255.255.0
 no ip route-cache
!
interface FastEthernet0
 no ip address
 no ip route-cache
 speed auto
 no keepalive
 bridge-group 1
!
interface Serial0
 no ip address
 no ip route-cache
 service-module t1 remote-alarm-enable
 bridge-group 1
!
ip classless
no ip http server
!
bridge 1 protocol ieee
!