My upstairs toilet flushes (most of the time) but my downstairs toilet is not flushing properly. We've just had a major snow/ice storm and was wondering if the "stink pipe" on our roof could be iced over and not allowing the air to come down. Any ideas?

That stink pipe is your vent stack, yes it could be a cause of this problem but other issues are more likley. Have you been able to plunge that toilet really well with a plunger made for a toilet and not a sink? Have you tried a tiolet auger yet? toilet auger - Google Product Search

Please answer ballengerbs guestions, we will try to help you out.