Anyone has any idea what could be happening with this thing... I know the modem works perfectly fine for anything else...I can download and upload any amount of data while the 16 units are running and nothing happens. But just starting a single extra unit after 16 and have it on a different miner software or adding the extra to cgminer will instantly crash the modem even if it was fine for hours before.
Crappy little routers with limited CPU power and not enough memory cannot
0. have an infinite state tables to do NAT and firewalling
1. swallow all the interrupts your packets generate
It's not about the bandwidth but about the amount of packets per second and how many concurrent TCP sessions that is causing your modem to hit a limit.
Is your modem also your router/firewall? Try to offload that functionality to another machine you can put in front of your modem and configure the modem as a bridge between PSTN/ethernet.