My roommate used to have a cat, and we tried everything. NOTHING ever worked 100% The best temporary solution was the most expensive. Take the cat to a veterenarian and let them bathe the cat in whatever professional flea killing solution they use. While the cat is gone, bomb your house with Zodiaque or the most brutal stuff you can find. Sweep, mop and vacuum thoroughly to get rid of the eggs in the carpet, etc.
As much work as that is, it\'s still not 100% effective.