I may have the same or a related problem. I have 2 linux boxes and one XP box on a gigabit lan. I get around 20-30MB/s (no jumbo packets) on most traffic. However, uploading from the XP to the file server just crawls at around 3-5MB/s. I thought it was the XP NIC (DLink 530) but I just upgraded (90% new guts) my XP box and the onboard Intel 1000 is exactly as slow as the DLink. I'm running FC3 on both linux boxes.
Here's the weirdness I see:
To
From linux1 linux2 xp
lx1 - fast fast lx2 fast - fast xp fast SLOW! -
I'm testing with NFS between linuxes and CIFS/Samba between linux/XP. I've run a test on the slow link with FTP and got the same result.
What I don't understand is how the results can be asynchronous.
I see no errors in ifconfig in linux. I tried a different (CAT6) cable. I tried a different switch port.