I Have a Windows XP Machine Running wireshark, connected to a Mirror port on a network. I'm capturing with no filtering, and it can only see half of some two way TCP conversations. I had thought it was a mirror port issue on the switch, but I can take the same ethernet cable, plug it into a laptop running the same version of wireshark and see both sides of the conversation. I also see a lot more random network activity such as NBNS queries, LLDP multicasts, and Dynamic Truning protocol packets.
This does not appear to be a promiscuous mode issue, because I do see half of a TCP conversation from point A to point B, and I am point C. I've tried replacing the network card but that isn't it. Its not random packet loss, because I see every packet for one side of the one conversation (based on sequence numbers)
I'm looking for any Windows configurations or other programs or clues that could be preventing Wireshark from capturing all packets.