Continued Network Magic problems

Hi there,
Have read and tried all forms of advice currently posted but still stymied.
Here’s the stats:
Comodo v3, Network Magic v5, Desktop Vista Ultimate, and Laptop XP Pro SP2

I’ve set up Network Magic and Comodo v3 on both machines and set all Network Magic programs (nmsrvc.exe, nmctxth.exe, nmapp.exe) as trusted applications. Unfortunately I still cannot share my files.

Here’s the thing: my Vista desktop can see files on my XP Pro laptop, but not the other way around. Network Magic claims that both computers are “online” and sharing properly, but when I try to open a desktop file on my laptop, I get the “Shared folder not available” error. Disabling my laptop firewall still doesn’t help, leading me to believe that, somewhere, my Vista desktop is denying an incoming connection, but I can’t find it. Any ideas? Possibly a router problem?