Oil fill cap blew off!

[canadianboy]

I'm hoping someone can share a little insight regarding the problem I had with my X5. It was about -30 degrees celsius going up to Visit my family, about a 4 hour drive. Pull into the driveway, shut the vehicle off and didn't start up until the next morning at about 10. After letting it idle for about a half hour, I was driving around town taking it easy then decided to accelerate momentarily. At that time i heard a pop and a slight smell of burning oil, pull into the driveway, lift the hood and notice the oil fill cap missing, and oil spray covering the hood and other components. So after a slight panic I phoned the local BMW dealership, they told me that the crankcase breather line had froze up and likely caused the cap to blow off. I can understand a little blowby coming from the engine but i didn't think that the engine could build up that much pressure. Anyway I took it to a shop I used to work at and let it thaw out for 12 hours. Only thing I've noticed is a Check Engine Light comes on sometimes. No real performance problems though. Does or has anyone encountered this problem before on any BMW product? Advice would be great!