COX keeps frying my modem.

First thing I would check is that your coaxial is connected to your ground at your demarc. Also check that there is no current back feeding onto your ground. I am not a electrician but I think it has something to do with when your neutral gets damaged, the next path of least resistance is the ground.

If you have a meter, check for AC voltage between the tip and sleeve of the coax cable.  You might also want to use a basic outlet tester to see if there are any problems with the way your electrical outlets are wired.  it sounds to me like you have an electrical issue somewhere.

Cox cannot own up to it, because the Coax doesn't conduct electricity, it's is an RF signal, and basically an antenna wire. Electricity requires 2 wires, positive, and negative, the Coax only has a single wire, the second layer is only a shield, not conductive wire. The ONLY time electrical current comes over the coax, is when there is an electric/lightning strike, and you SHOULD have a ground tap outside to prevent that. 

Next, does your surge protector have a ground detector, to ensure that neutral and ground aren't reversed on that outlet. If it is, that could cause your issues. 

Mine fried at exactly 7am and had worked fine for years - top tier Arris modem -  been through several days of intermittent outtages and bam, dead at 7 am. Call support,first they play like they can’t get my new Arris working, so they have to connect me with the sales dept, no thanks. Chat up cox and raise hell and suddenly they can activate my modem. Greedy thugs with a monopoly.  yes, they fry modems.