We have several Windows 7 PC's (2 running Windows 7 Professional, one running Enterprise edition all have SP1 loaded) that when you run a PING the cursor moves down a line and blinks then the Command prompt comes back without having displayed any successes or failures. The firewalls are all set to allow ICMP in and out. And I can see the packets in Wireshark going in and coming back. Any ideas?

It sounds like your output is being redirected. Instead of typing in just PING computer, try using PING.EXE computer instead. If that works, search for a PING.BAT or PING.CMD file somewhere in your path and delete it.