vlans between 2848 and 2824

Hi, we have a 2824 and a 2848 connected to each other via fiber on port 24 and port 48 respectively.

Now we are trying to create a separate VLAN for use by a couple of people.

I created VLAN 13 on both switches, and changed the PVID on ports 20 and 40 respectively on each switch to 13 so that they now show as "U" for vlan 13.  I also added VLAN 13 as tagged on ports 24 and 48 respectively.

Port 20 on the 2824 is connected to a firewall interface at 192.168.169.1 and port 40 on the 2848 is connected to a laptop at 192.168.169.4 - we are unable to ping across.  Any idea on what we've done wrong?

Thanks!