If using cnMaestro, run the WiFi Analayzer for the router. You should see any conlficting AP's there. Change the channel manually. Devices such as Roku's will purposefully take the same channel as other WiFi. When the R190's experience really bad interference the DNS Proxy seems to turn off. So best turn off the DNS proxy and manually assign the DNS for DHCP.
Check this for other info. http://community.cambiumnetworks.com/t5/cnPilot-R-Series-Home-Small/cnPilot-r201P-terrible-throughput-when-connected-via-wifi-hard/m-p/117095/highlight/true#M2103