iChat does uPnP, bet Netgear's implementation is really buggy. According to a post in the Apple message boards, this works:

1. Open the Netgear SmartWizard router manager in your browser

2. In the Advanced menu select 'Port Forwarding/Port Triggering'

3. Select service type by clicking on the 'Port Forwarding' button

4. In the 'Service Name' pull down menu select: AIM
The following should already be entered in the table: Service #1: Service Name: AIM, Start Port: 5190, End Port: 5190, Server IP Address: Your Server IP Address: e.g. 192.168.1.2
Click on the 'Add Custom Service' button and input the following:

5. Service #2: Service Name: ichat 1, Start Port: 5060, End Port: 5060, Server IP Address: Your Server IP Address: e.g. 192.168.1.2

6. Service #3: Service Name: ichat 2, Start Port:16384, End Port: 16403, Server IP Address: Your Server IP Address: e.g. 192.168.1.2