Caution when using Netgear PowerLine adapters!

Powerline adapters such as AV200 can cause havoc with BGW210 modems: internet traffic virtually dies.

History:  Old modem was connected to a 16 port switch.  One of the ports on the switch went to an AV-200 PowerLine adapter adjacent to the switch.  Five rooms in house had matching AV-200 and all worked fine.  

The old AT&T modem died: uVerse and Internet not working.  AT&T technician came out and replaced the broken modem with BGW210.  He first disconnected the 16 port switch and verified the uVerse TV was working: It was.  Before he could connected the 16 port router to the back of the modem one of my kids yelled that the internet was back on.  After about 15 minutes of trying to figure out how we got internet when the modem was not event connected to the switch, the Technician discovered the built-in WPS of the new modem was automatically connecting to the AV-200 PowerLine adapters.  OK, he then connected the 16 port switch to the modem.  We verified the hard wired devices on the switch were working and he left.

Within minutes the internet slowed down and eventually came to a halt.  By unplugging various systems I discovered the problem was that original AV-200 that connected the 16 port switch to the wall plug.  Apparently it was caught in a loop back or feed back mode (I am guessing) since both it and the modems WPS were feeding the other five AV-200 units.  They must have some conflict with each other???

After that AV-200 was disconnected the internet instantly was back to its normal speed. 

I actually do have a question:  The devices on the AV-200 (One mac, two linux) can ping each other but not any of the devices on the 16 port switch.  Vice-versa, my windows 10 system can ping another of the other devices on the 16 port switch but cannot ping the devices on the AV-200 anymore.  However, the surface pro that is on WIFI can ping any of the devices.

Would be nice if someone can figure out what is wrong as I would like to share files, not just "ping".

[EDIT]

There is no builtin PowerLine in that AT&T modem, I was mistaken.  Here is the real cause of the conflict:

The BGW210 connects to a VEN501 AT&T wireless access point "WAP" that connects to the CISCO TV adapters provided by AT&T.  Those CISCO adapters are in each room that has a TV.  Each of those CISCSO adapter has a single ethernet port that can provide internet access and is not just dedicated to providing uVerse TV as I and the AT&T technician thought.  I had connected that port into a 5 port switch that had a linux system, printer and a Samsung TV.  I then connected the 5th port to the wall using the AV-200 as I thought I needed to get ethernet.  I did not know the CISCO provided internet that it obtained from the VEN501 WAP.  

My solution to fix the printer access is to remove the CISCO ethernet wire from the 5 port switch and put the AV-200 back onto the 16 port switch that is fed by the AT&T modem.  That way all the AV200s are fed by a single one that is on the 16 port switch.