Hi Joe,
It would be good to know the type (and software version) of firewall as it
could be the firewall and not the switch that's the problem. For instance,
there's a known bug with checkpoint and NAT where automatic arp entries
"disappear".
If you can ping it all from the catalyst but not from the rest of your
network it could be that you have a problem with your dynamic routing
protocols, or with a device connected to the catalyst. Check your adjacent
routers, do you have a valid route to the catalyst for the 192.168.5.7
subnet? What does a traceroute show from your NOC?
-GP