Problems with file transfer

[azog]

A friend and me are having some troubles using file transfers with Yahoo Messenger (6.x). We can do voice and text chats in either direction (he can call me, and I can call him). It's just file transfers that don't seem to work.

When I try to send him a file, he gets an error message to the effect that he cannot receive files, and may be behind a firewall. I get an error message "user cannot receive the file blah directly from you".

The same in reverse - when he sends mea file, I get the firewall error message, and he gets the cannot receive message.

We're both behind firewalls (actually cable/DSL routers w/firewall firmware). We didn't need to configure anything special for voice chats, so the Yahoo help pages (which say open port 80, and some other ports in the 5000 range) don't really help. And yes, we did do their configuration and open these ports, Just In Case.

I sniffed the session with Ethereal, and found an interesting packet (just the relevant header):

No.     Time        Source                Destination           Protocol Info
      3 7.630548    192.168.0.3           192.168.2.50          TCP      1116 > http [SYN] Seq=0 Ack=0 Win=65535 Len=0 MSS=1460

The source is me, 192.168.0.3. The destination, 192.168.2.50, is him. This is obviously incorrect, and might be the problem.

Does anyone have any ideas?