Check your duplex. I have had two recent problems with duplex:

One, with a Cisco router - it auto-negotiated every time to half duplex, even though it really -was- full. Use mii-tool to find out.

Two, with a RR modem - the speed was forced to 10mb half duplex instead of 100mb full duplex. All sorts of strange loss. Once I put it back, all was well.

I have used TONs of 8139s, and while I do see where they are not the fastest kid on the block, I cannot say I've seen packet loss.

Bob