I'm seeing a similar problem with a 3CCFE656BT card. I found that the card performed much better if I did something like:
ifconfig eth0 mtu 350
This sets the maximum packet length... the default for ethernet is 1500. I still don't know the reason for the problem, but this seems to help a lot, for me anyway.
(it seems that if more than a couple big packets are queued up for transmit, the card chokes and sends out damaged packets)