Problem with sirius plug-n-play

I hardwired a 12v to 5.5v adapter between the back of the cigarette lighter and the sirius radio. It works, but seems to have to a have a problem related to power surges. If, for example, I put the windows up, or the ICE kicks on, the radio will turn off and won't turn back on for a minute or two. I've tested the voltage at the radio and it's getting 5.5v throughout, even the when the radio is off and wont turn back on. It seems like a spike in voltage is causing the radio to shut down and remain down for a set period of time.

Anyone else seen or heard of this?

My step father is an electrical engineer and said that all cars have "noisy" electrical systems, and the prius is probably more "noisy" than most, and the 12v-5.5v adapter I installed might not be able to handle it. I have little idea what "noisy" means, but it seems to makes sense. I have the same exact set up (same radio and power adapter) in my Blazer and it works fine.