This is an area where we remove what we can do without to narrow down the possible bad parts.
If it is the router, new or not does not matter. New routers arrive with out of date FIRMWARE. We also see a lot of people follow some pundit's advice and disable SSID broadcast. Sorry for WIFI I find that enabling this helps and for security we use WPA.
Good luck but given so little to work with I have only this to share.
For the last couple of months we have had problems with our cable interent connection with Comcast.
We have a desktop PC which has the cable modem, linksys router and a digital phone adapter, all of which are relatively new and were working fine until a couple of months ago. Comcast have been out and replaced cable ends and spliter, but when they were here it was working. Its irregular with its connection, it could be working for 5mins or 5hrs and the go out for who knows how long. I can reboot modem etc, it might work or it might not. Comcast dont know whats wrong and neither do I.
Anyone have any suggestions or fixes?