Issues with FIOS modem/router's wireless and multiple devices connected to the WLAN?

Question

I am an IT consultant who was assisting someone with getting some devices connected to the fios wireless router and adding a wireless print server so they could print wirelesly. 
I was having difficulty with one of their systems that was connected prior to me going on site.
It was having difficulty obtaining an IP from the WLAN, i tried reinstalling the adapter, removing stored wlan settings and setting it up again, etc.
When it did obtain an IP it could not ping the router.
I had left it suggesting that they replace the wireless adapter on that system.
However they're saying that after they shut down one of their other devices that i had connected (a netbook), that this problematic system started working fine.
It makes no sense that a wireless client would have an impact on another wireless client. We're only talking 4 total devices here, a netbook, a laptop, a wireless print server and a desktop in another area of the house that has a usb wireless adapter.
Does anyone have any ideas on if Verizon's wireless built in to the fios modem/router just isn't too good to handle multiple wireless devices?
After hearing this i was thinking they might have been better off configuring the fios router as a bridge and getting a better wireless router or shutting off the fios supplied wifi and implementing a wireless access point instead of using the router/modem that verizon provides.

Answer 1

By bridge I mean in the sense you see some of the early DSL setups configured before they started using multiport routers -- essentially bridging the WAN MoCA port to the LAN ethernet.   The ActionTEC's won't do that.   This is what I think most are seeking to do when they want to turn the device into a "bridge" (essentially making the Verizon unit "transparent" to the communication which in this scenario it can't be).  You can do as suggested an turn the ActionTEC into essentially a "switch/bridge" that is only bridging the MoCA LAN and Ethernet LAN segments, but this then requires you to have an ethernet WAN feed from the ONT ... and as indicated, it is definitely not a "supported" configuration from Verizon (although there is nothing "wrong" with doing it this way if you are comfortable with networking and understanding the mechanics of all that is going on -- if not, sticking with a supported configuration is highly advisable).