I agree with the first answer - a recent short sale that I completed took over a month for the bank to respond - the lender is going to evaluate very closely whether the Seller really has no assets to pay for the difference before they are going to say yes to a short sale - although I do not think the lender will drag their feet deliberately, the lender is also hoping someone else will submit a better offer than yours while they are doing their research on the Seller. In today's market, there are Sellers who have a home that is worth less than the mortgage and even though they signed a contract to pay back the loan, the Seller is hoping to dump the home on the lender. If you were the lender, you would want to make sure the Seller really has no assets before accepting an offer that was less than what is owed.
I recently had a title company closer tell me that the longest short sale she has seen was 14 months (don't worry, most will not take that long) - as Realtors, we need to guide our Buyers that while a "short sale" home may be attractive to a Buyer, they are not for the Buyer that does not have a flexible current living situation (for example, renting on a month-to-month basis) because they will take longer and the lender does not care what "closing date" is put in the contract.
If that home is the best home for you, then I would make sure through your Realtor that the listing Realtor is making contact frequently with the lender (a minimum of once per week) and be patient - the lender has no obligation to you or the Seller to move quickly on the file. I would continue to look for other possible homes and let the listing Realtor know that you are doing so (hopefully you have a clause that allows you to terminate the contract for the "short sale" home if you find another suitable home while the lender is deciding what to do).
Additionally, for you and others who might be comtemplating a "short sale purchase", please make sure that all of the dates for completing tasks (like the inspection) go into effect after the lender has agreed in writing to the proposed offer because you as the Buyer do not want to be spending money until you have greater confort that the house will actually change possession - this can be accomplished through an amendment if necessary. Good luck!