A couple of ideas:
1. Pam is right, talk with the relocation dept. and see what they can do. A good relo dept. understands that smoothing out the wrinkles in a move might involve more than it used to (meaning they may have more flexibility than they did in the past).
2. You might want to read my four-part blog on short sales and foreclosures. The bottom line in your case is that a lender would rather have you sell it for less (a short sale), than foreclose. However, if you have any other assets (401K, for example), the lender is going to want YOU to participate in the loss.
3. You might want to consult a CPA regarding the impact of renting the home if you cannot sell it. My wife and I became accidental investors way back when and it turned out to be a real blessing.
Speaking of credit scores:
Worst - BK or foreclosure - cannot buy a home for probably 5 -7 years
Next worse - short sale - tax implications (10-99 for the amount forgiven) and a "ding" that, if you already have some problems, might make purchasing a new home a tough go.
Good case - You might be able to re-negotiate the loan terms. I encourage you to talk with your lender. Most lenders are becoming very concerned about the loans they have and will prefer to work with a willing owner than conduct a short sale.
Best case is to hang on and rent it out (if you can handle the negative cash flow....which is why you need to talk with a good CPA (I am NOT a CPA).