I just got a new laptop, and for the most part have left its settings alone. Today I was trying to get some sharing going between my desktop and the laptop. Both machines are connected to the same wireless network and both machines consider that network to be a Home network. Both are running Win7 Home Premium.

It seems like my laptop is aware of my desktop on the network. It can ping it by IP or by computer name. When I go to Network from the laptop, I can see the desktop in the list of computers. However, my desktop cannot ping the laptop, nor can it see it within Network. My desktop has a Homegroup set up, but my laptop says "There is currently no homegroup on the network".

I do have network discovery turned on for both machines.

Why can my desktop not "talk" to my laptop but it works the other way around?

Update:
Disabling the Windows Firewall on the laptop somewhat fixes the problem. With it disabled, my desktop can ping my laptop, but still my laptop can't see the homegroup. Also, it can ping via hostname, which resolves to IPv6, but can't ping via the IPv4 address. Obviously I'd rather not leave my firewall disabled, so I need a more specific fix.

Update 2: Aha! It is the Cisco VPN software I was running to connect to work computers. Once I disconnected and exited from that, the two PCs seemed to be talking normally and the homegroup was visible to the laptop.

So now my question has morphed: how can I prevent Cisco VPN from interrupting my home networking?