Making an offer on a short sale property can require a great deal of patience depending on who the lender is on the property. Some lenders process the short sales within a 30-60 day timeframe, while others can take 90-120 days, if not more. Each lender has their own processes and timeframes. In addition, if the home you have made an offer on, has more than one mortgage, it then requires the approval of both lenders.
Staying in touch with your realtor and having him/her stay in contact with the office handling the short sale is crucial. Sometimes it requires following up with the lender every week to make sure that all is progressing forward. Sort of the sqeeky wheel gets the oil thought.
Good luck and of course be patient, it really can be worth the wait.