New day, new problem. 

I'm using the Steinberg UR28M interface, which is noisy anyway but when Sonar X1 opens my goodness it takes noise to a new level. Have any of you experienced this? I hope it's something really dumb and simple that I'm missing.

Are you joking? Sonar XL? 

Sorry, fixed. X1

What kind of noise?  If you could post it that would help, but a good description might work too. 

Have you ever had a noisey light that just kind of buzzes and squeaks. Sounds like electrical interference or something.

Simple solution is turn your monitors down before opening Sonar.

  That said...  what do have hooked up to it when this happens?

Edited: because apparently I can't read. 

could be grounding / earth loop..  I'm assuming you have cubase also ? or some version, does it give the same sort of noise.. if so, it'd point to an the hardware not the software..

make your default windows device ya realtek card in windows control panel..

in sonar, make your steiny interface the one you use + asio... also be sure to untick other things off input / output wise, otherwise you can't use asio mode.

if you must use that as your main soundcard for everything, use WDM mode I guess.

When my computer is on and I turn my reference monitors on I get a little bit of noise. Not too bad, I could probably live with it. As soon as I open Sonar, before I even load a song all kinds of electric static starts coming out of my reference monitors. It's the craziest thing.

sounds like your shielding or a grounding issue.. if you are using a laptop.. try from without the mains adapter.. if it's not doing the same, then it points to that.. 

are you using a gang adapter to split the wall socket to 4 etc ? cheapo ones again can cause issues

you need to give a lot more info.. mind reading skills aren't great.. what type of pc.. and speakers.. you using the right sort of cables balanced / unbalanced etc.

Check your levels on the UR28M  and your monitors. Try uninstalling the drivers and reinstalling them. Also when reinstalling move the USB to another port.