You want to do water changes, water changes and oh yeah, more water changes. You're not the first to have cats (or kids or spouses or insert reason here) knock over the CO2 bottle or otherwise cause the mixture to get into the tank. It can kill off the fish if left unattended, but I gather your tank is fishless from the last line, so that's not a concern. The big concern is the cloudiness and smell caused by the mixture getting in the water. Keep up water changes until the cloudiness clears or as the smell bothers you. There also could be secondary bacteria blooms, algae problems and wierd fungus strings according to some reports while the issue stabalizes.
And here's an archive of Usenet/mailing list postings on The Krib by others in your boat, just so you can see you aren't alone
http://www.thekrib.com/Plants/CO2/yeast-disaster.html
In the future, you might consider making a bottle holder out of the plumbing 'tape' (half inch or so wide metal with holes) that is used to attach water heaters to walls. Make a circle big enough for the bottle then attach that to the stand (or wherever is convenient for your setup). This should prevent the cats from toppling the bottle in the future.
