Cisco WAN :: 2901 To ASA 5510 Via Leased Line Poor Throughput

I have two sites connected via 2901 routers to a head end with an ASA 5510, the WAN circuits are LES running at 100MB and at the head end we have a 100MB leased line.  All WAN circuits are provided wires onlyby another supplier.  I have setup the two 2901 routers with inside IP addresses on GE0/0 and a /30 subnet for the GE0/1 interfaces to the ASA over the LES circuit.
 
The LES circuits are set to 100MB but the problem I am having is that one of the 2901s will only negotiate at 10MBps Half Duplex with the ASA at 100MB Half Duplex, the other will negotiate at 100MBps Full Duplex at both ends.  My WAN provider tells me both LES circuits are the same so I cannot work out why one will negotiate at 100MB Full and the other at only 10Mb Half.
 
At the head end I have and ASA 5510 connected to the WAN providers 100MB circuit but testing from my end sites I can only get 6MB download and 0.5MB upload on an Internet Speedtest.
 
I used Wireshark when downloading from my end sites and I can see lots of TCP retries and duplicates so I think this is a duplexing issue, my question is, my WAN provider is stating the issue is nothing to do with them and it is my 2901 and ASA that is at fault, they state if they connect a laptop to the LES circuit and then their leased line they get 100MB up and down.