Any reason why my imac might show up as a PC in Leopard's sidebar?
Also, when Windows computers appear automatically in the sidebar they have the BSOD icon, but when I use "connect to server" they have a cinema display icon. Seems odd all round.
that icon is for SMB. do you have only "SMB" check in the Options of File Sharing preferences on either Mac? AFP will know which Mac it is by using Bonjour and show the right icon.
PCs will always show as BSOD icons as you use SMB to connect. and Connect to Server will always use the Cinema Display icon.