If both amps are failing at the same time, chances are, you're dealing with something impacting both amps.
Possible common causes are AC power, input signal, or USB signal.
AC power is probably the most likely. While a full power outage will cause the amp to reset and it SHOULD come back on in the same state that it was in, partial shutdowns, or sudden voltage swings could cause the CPU to get confused and do weird things.
An input signal that has an issue, such as DC bias on the signal might cause a problem, although I've never seen that with this amp.
If you have the devices connected with USB, you could be remotely triggering a shutdown. If you don't have them connected to a computer, go ahead and do that. Then you have detailed monitoring that could help determine what the problem is.
The power conditioner you are using is only a fancy surge suppressor. It will clamp down voltage if it goes above 140v. It doesn't 'condition' in any way other than that. It's only rated for 15 amps, so if you pushed the 4.5's hard, you'll be well above that. Still, you'd simply trip the breaker. The conditioner itself shouldn't be a cause to this problem, unless for some reason the circuitry inside is creating some weird harmonics messing with the amp. (very unlikely)
If heat were the issue causing this, it seems extremely unlikely that both would fail at the exact same time.
