I recently had a problem with my A/C and found a few very helpful troubleshooting sites for common A/C problems. I'll see if I can find them for you. In the meantime, google for "home air conditioning problems" and variants.
Check the intake filters on each floor. Is the inside unit's blower running? Is the condenser fan running in the outside unit? Is the compressor kicking on in the outside unit?
I live in Seattle and only know a couple people with A/C. And believe it or not it does get pretty warm up here. I think most people are too stuborn to buy something they'll only use a couple months out of the year.