Short sales can be fastracked for lender approval (if the listing agent knows who to send A COMPLETE PACKAGE* to and forwards it to the right contact person at the lending institution). It is not up to your buyer agent but rather the listing agent and the attorney (depending on state laws) working the file to contact the bank for updates (the bank will not speak to anyone who does not have written authorization from the homeowner). An experienced agent can get an answer (acceptance, rejection, or counter offer) in about 30 days. A newbie could take months before putting two and two together.
However, i should point out that if there are TWO mortgages (first and second liens) then the process of negotiationing between both lenders could take several months. My first short sale with two lienholders took about 7 months (buyers were patient and followed through).
If your buyer's agent wasn't clear in this explanation then it is likely because he or she has little to no experience in these matters. He or she should have explained that it will take some time, however, i have worked with agents that have gotten approvals in as little as 10 days (yes, i was shocked).
Check your contract and look for a closing date. Technically, you can walk away after that date. But until then, this is a legally binding agreement and you will have to wait it out.
You have to be patient with short sales. And funding for most homebuyer assistance programs usually (at least in my state) kicks back in January 1st.
Talk to your agent without driving him or her nuts. I don't want to violate realtor ethics here, but if he or she isnt providing you with answers in a timely fashion, and if it seems like he or she has little to no experience in this arena, then look for a qualified agent who can provide you with quality service once this contract does expire.