Ok, here's the deal. It is about 0 degrees out and my 850R had been outside for about 5 hours since last running fine. I went out and started it up... no problem.

I put it in gear and tried to accelerate... nothing. The rpms wouldn't rise above idle, but the gas pedal did move. It would drive, but just like if you let off the brake.

I got out and pulled the throttle cable a bit and the rpm's did vary. I let the car sit for about 5 minutes until it heated up. It then began to allow more and more throttle, until it finally ran somewhat normal.

So, sounds like a frozen throttle cable... right? Anyone had a similar experience?

What I HAVE seen that causes your problem is that if you have an old, weakened oil saturated intercooler hose, the hose colapses when cold on accel. If that's happening, you can see it by watching the hoses when opening the throttle.
The solution to that is to simply replace the bad hose IF your dealer has one in stock (might need to be ordered).
An intercooler hose might also have a hole in it too but if so, acceleration would still be bad when warmed up too.
The hoses on all turbo cars eventually weaken, deteriorate with age because what IS inside those hoses is a slight oil mist, normal on ALL turbo cars and that oil eventually disolves the rubber hoses from the inside.
If any intercooler hoses look oily and/or are weak and spongy feeling, they should be replaced.

farenheit or celsius , if its farenheit your intercooler is probably frozen and air cant pass thru , leave your car running for approx half hour at idle , all the humidity inside the cooler will go on your driveway by the drain hole at bottom of the intercooler dont worry if its browncolor , its a mix of oil and water , oil is considerd normal with a turbo engine , perform research here to found solutions ,,,,
if it can help

You've actually seen that occur? I havent and I not only own an old 745T BUT have been a Volvo tech in a northern climate for 20 yrs. There is not really much moisture ever in an intercooler as I've never seen more than a few drops ever drain out of one and older 700s had intercooler drain plugs. Mostly, just air passes through intercoolers.
I've read where a person or two here has recently claimed that here but is that really what's happening? I have my doubts. If it is happening somewhere (like maybe northern Canada?), what's the solution?