Hi,
On the PC in the Firewall (Start > Control Panels > Firewall), have you set Pidgin up as an Exception ?
Bonjour, as Apple's Zero Configuration, method connects on Port 5353 on the UDP Protocol.
iChat Bonjour uses this plus port 5297 on UDP and also port 5298 on TCP and UDP.
Essentially Text Chatting takes place on one port and File Sending on another.
The Windows Firewall is likely to Allow Outgoing Stuff but not Incoming stuff.
9:20 PM Monday; October 18, 2010
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"