laptop can connect to desktop, but not vice versa

The basic problem: My laptop can connect to and see shared folders on my
desktop, but my desktop cannot connect to or see shared folders on my laptop.
In My Network Places on the desktop, I can see the laptop, but when I click
to browse I get the following error: "\\Laptop is not accessible. You might
not have permission to use this network resource....The network path was not
found."

More information: Both desktop and laptop are running WinXP Pro SP2. They
both connect to the internet through a wireless rotuer, which is connected to
a Vonage router which is connected to the cable modem. I ran the network
wizard, setup a workgroup, set my firewall (Kerio) so that the IP range was
in the trusted zone. I am using simple file sharing on both computers.

Any ideas, experts? Thanks for your consideration.

=?Utf-8?B?bnRhbmNyZXRv?=