When I booted up my computer for the first time this morning, I got a
system message like "System Shutdown, ... NT AUTHORITY/SYSTEM, ...
Remote Procedure Call termination..., computer will restart in 60
seconds"

Then a connection box appeared saying that "dynamicnet.ath.cx" is
trying to connect to the internet.

All I could do was to use system restore to remove whatever it was.
But I would like to know exactly what caused this and if it was
dynamicnet.