On the 'Services' page in the Shub's advanced settings, untick 'Firewall Features', 'Port Scan Detection' and 'IP Flood Detection'. You may as well also set the MTU to 1500 manually and tick 'Respond to ping' on the 'DMZ Host' page and turn on UPnP in the relevant page as well. Remember to set up your wifi security to WPA2 AES only and manually select a free wifi channel (scan with one of the free tools you can google up on your wireless PCs or using a similar tool on Android phones).
Update your PC lan drivers if available. Check any wired connections. Try a different piece of ethernet cable if you can. If you are actually losing network connection to the router on a wired connection with a known good lan card and ethernet cable then the Shub may be faulty. Get a replacement.
By the way, the Shub is using then new Shub power supply isn't it? Not the old one from your previous modem...?
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