Sounds like a nightmare. Your only mistake was booking a flight on Air China (even though it's got a UA flt number)--I'm not sure I'd trust any of the Chinese airlines. Customer service is still an unknown concept to them. (And we complain about UA????!!!!!!???)

I'm not sure UA can do anything for you--you are on a UA ticket, but UA's going to claim that they're not responsible for what CA does, and to a large degree that's true, particularly if CA claims it's weather related. Your 1K (*A Gold) status probably doesn't mean much to CA. Your best bet at the moment is to ride it out. My guess is that there aren't many flights btwn HKG and PEK at your time of the morning--if it gets to be 6 or 7 AM and still no flight, try calling UA and see if they can put you on another airline--but my guess is right now you're stuck.

Good luck! Keep drinking the Bailey's.