All my Windows 2008 server are giving me the same symptoms. When an XP client access their shares, and they upload a file, speed is good. When they download a file, speed is bad... very bad (around 5 times slower).
If the same client do the same test with the same file on W2K3 servers, we have no issues at all in both directions.
All the servers are in the same rack, on the same switch.
One more interesting fact, if I remote the server and do a file transfer from the server to the XP machine, I get no problem at all (up and down).
Transfer with netcps are fast and furious. I know it's something related to smb windows shares, but what!