Communication is the key. Try to talk to the Buyer's agent and see what is going on. At the same time I would prepare a 24 hours to preform notice, it is on Winforms, just in case, and alert your broker and the title company. Hopefully you won't need any of this, and it will all be resolved, but it is best to be prepared. Keep trying to get the lines of communication open.
The "notice to perform" may be given up to 2 days before the deadline. I would have it made out, signed by the seller and ready to go at that point. The buyer will either need to perform, or you can ammend the contingency removal deadlines. If you don't do that, the seller may come after you for not protecting their interests! If the buyer has a legitimate reason to delay, consider giving them some more time, but if that buyer can't close, it's best to get the property back on the active market ASAP!
I wouldn't do anything until after the contingency period is up (provided I have been in communication with the buyer's agent and everything looks on track) and then I would send a notice to perform. If there are problems with some of the contingencies, I would try to get the buyer to remove some and work with them if at all possible. Contingencies need to be removed in writing by the buyer.
The Reavis Group @ Keller Williams Wilshire