VLAN setup on 3348

I have a PC 3348. Machines plugged into it will be on the 192.168.50.x subnet (a test environment). The switch will connect to another switch that is in our DMZ - this switch is on the 192.168.5.x subnet. Thinking I understand this, I set up a VLAN, gave it an address in the 192.168.50.x subnet, and used that IP as the gateway for the machines in the test environment. Most of the ports were assigned to this VLAN, a couple I left in VLAN1. VLAN1, the default VLAN, I gave an IP address in the 192.168.5.x range, and set its gateway as the IP address for the other switch in the DMZ. Before I plugged it into the DMZ switch, I plugged another machine with a 192.168.5.x address into one of the VLAN1 ports. When I ping from that workstation (on the .5 subnet), I can ping the Test VLAN address (192.168.50.x) successfully, but get timeouts pinging any of the machines on that subnet. Likewise the other direction - fromt he .50 subnet I can oping the VLAN 1 address (192.168.5.x) but not the .5 machine. There are no access lists in place, and nothing on the client machines that is blocking traffic. What am I doing wrong?