I've paid the judgement against me. Can the plaintiff still foreclose on my house?

Not sure what receipt you have from the county clerk's office, unless you mean a receipt for filing of a satisfaction of judgment.  At any rate, if a judgment has been satisfied, it can't be foreclosed upon.  Even if there was a judgment of foreclosure (as opposed to a money judgment which is being foreclosed upon), most jurisdictions allow you to prevent foreclosure right up until the last minute if you pay the debt, although you may have to pay additional costs and fees.  You should take whatever steps you need to make sure that everyone involved (creditor, court, auctioneer, etc.) receives proof of the satisfaction.  From what you've written, I'm not sure you've sent proof of the satisfaction, as opposed to proof of the FILING of the satisfaction.