Windows – Window 8 machine cannot ping devices on same subnet

After returning from vacation during which several Windows updates were applied and my router suffered a hard power cycle, my Windows 8 Desktop can no longer ping other devices on the same subnet. Specifically:

• Win8 can ping the router
• Win8 can ping google.com (no internet connectivity problems at all!)
• Win8 cannot ping a Win7 laptop, Android phone, or Airport express on the same network
• Router can ping the Win8 machine (and all other devices)
• Other devices cannot ping Win8 machine

Since the Win8 machine can ping the router and google, I don't think this can be a firewall setting issue (I have tried it with Windows firewall on and off), or a Private/Public network issue.

When the Win8 machine pings any local devices, ping returns 'Destination host unreachable' and the target IP winds up in the ARP cache as 'invalid' entries, with MAC Addresses of 00-00-00-00-00. I have tried adding a static ARP entry to the Win7 machine, but all that does is change the ping response to 'request timed out' instead of 'destination host unreachable'.

The Win8 machine's routing table looks normal to my non-network-techie eyes (the subnet in question is 192.168.1.*):

IPv4 Route Table
===========================================================================
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0      192.168.1.1      192.168.1.6     20
        127.0.0.0        255.0.0.0         On-link         127.0.0.1    306
        127.0.0.1  255.255.255.255         On-link         127.0.0.1    306
  127.255.255.255  255.255.255.255         On-link         127.0.0.1    306
      192.168.1.0    255.255.255.0         On-link       192.168.1.6    276
      192.168.1.6  255.255.255.255         On-link       192.168.1.6    276
    192.168.1.255  255.255.255.255         On-link       192.168.1.6    276
        224.0.0.0        240.0.0.0         On-link         127.0.0.1    306
        224.0.0.0        240.0.0.0         On-link       192.168.1.6    276
  255.255.255.255  255.255.255.255         On-link         127.0.0.1    306
  255.255.255.255  255.255.255.255         On-link       192.168.1.6    276
===========================================================================
Persistent Routes:
  None

The oddest thing to me is that the Win8 machine can ping the router, and the router can ping the Win8 machine, which seems to eliminate most solutions I found with 2 days of goggling.

Any suggestions would be greatly appreciated!