This is not an attack. This is having to do with his link connection with the Modem and configuration of the router. Seem that he has alot of wireless devices are are connecting and then disconnecting.
He needs to turn off ALL wireless devices and connect up one wired PC and view the status while all devices are off. DO some testing and see how the router reacts. I would also turn off the Wireless and see how the router works. Any disconnections after wireless radios are turned off?
Then turn on the radios and then bring up one wireless device and test. Progress to the next devices and see how the router works out. Keep viewing the logs and status pages. Look at the Status page and see if you notice any status on the WAN IP address, does it say connected or connecting? Just making sure the wired connection to the modem is stable here too.
Does the 320B modem have a built in WiFi? Havn't seen this unit before. Keep us posted. Lets have someone use
Teamviewer.com and help you review your router settings.