I've got a 5500 that I cannot get to connect via USB-TCP/IP. I can get it to connect via USB-I/O. I can get it to work via TCP/IP on my home computer (XP Home SP1), but not on my work PC (XP Pro SP2). It used to work fine until I upgraded to SP2. I've got the firewall disabled, I've got all Zaurus apps set as exceptions, I've got the firewall disabled at each connection, and all services enabled on each one of those connections. In other words, even if the firewall were enabled, it wouldn't (in theory) be doing anything.
Yet I still cannot connect. Therefore, if any of you are using SP2 and have your 5500 or 5600 synching correctly via USB-TCP/IP, please post your Windows Firewall setting (network settings would probably help too).