MBPr shown to be connected to the net, while the router doesn't response to pings
I am experiencing the same problem.  The issue is the router.  There are a number of reasons why the router would do this....memory of the router is too small, too many connections for it to handle, to just poor quality components.

The way you can verify that it is the router is by


Pinging the router (which you did and it failed)
Pinging another device on your network
Test connectivity from another device


As for as your WiFi indicator, having full bars has nothing to do whether it has network connectivity (getting an IP address and being able to browse).  The "bars" indicate signal strength and signal quality, which both relate to the physical radio connection, not the network connection.

If you are familiar with the OSI model, it is layer 1 and 2 that your "bars" are reporting back.  Layer 3 is where your connectivity comes into play.  Think of it like how your (wired) Ethernet adapter  determines whether you have 100MB or 1GB connectivity



What's the solution?

Get a good router; or better yet, build it yourself.  I am finding that the consumer grade stuff is getting worse and worse every year so I decided to make a change.  

I recently built a pfSense router on some old Dell hardware and installed an Intel PCIe AC Wireless card and with all my testing, I have yet to have the problem reoccur.  

There's even a good YouTube video on this:  pfSense: How to Turn an Old PC into an Epic Router