I should also add that on both the Mac and the W7 machine you can use the "net" commands on the command line (the syntax differs between each OS) rather than the GUI, this makes troubleshooting a little easier.
On your W7 box type "net use /help" for a bunch of options including being able to specify a FQDN as a target host rather than a WINS/NetBios hostname. I can't remember if it works with an IP address, I got a feeling it doesn't.
Make sure the host name you use can be pinged, and try "net view \\yourmachost" to see if the advertised shares are even visible.