By seeking another appraiser, I was referring more to the idea of getting another opinion. Banks are getting more in tune to what is going on in and what homes will sell for. They usually want to avoid incurring the costs and headache of foreclosure.
Again-Good Luck!

Don't panic! This actually could be good news for you. The seller's bank truly does not want to have to foreclose on that house - They stand to lose a lot more money if that happens. Cross your fingers until the seller is given a chance to renegotiate with their bank, based on the appraisal. Things usually work out. If not, then cross that bridge when you come to it.

Sure. The seller's bank can refuse to allow the short sale. On the other hand, an appraisal is a powerful argument for reducing the price to the level of the appraisal.

However, although Jennifer's answer is entirely correct, I'd be very cautious about simply looking for another lender, or searching out a higher appraisal. What if that first appraisal is correct? What if it's not worth as much as you've offered? Do you really want to overpay for a property in today's market?

Ask to see the appraisal. You and your Realtor should go over it, and your Realtor should pull the comps in the area. Determine what the property is worth today. If the appraisal isn't justified by the comps, then your Realtor can advise you on what next steps you should consider. But if the appraisal is justified, then you might want to rethink your offer.

Hope that helps.

The seller's bank could refuse. That is the unfortunate part of a short sale. I would recommed that you explore another appraiser. This may require you to use another lender. Good luck- I hope you get your dream home!