I'm posting this both as a warning to carefully read every single line of letters your lender sends (even when you think it is a duplicate copy) and to ask if anyone else has had this happen to them, and if so how it was resolved. Here's my story:
After 5 protracted months of struggle including an unjustifiable denial of HAFA, Chase (servicing for Fannie Mae) finally agreed to give me a "traditional" short sale. The unnecessarily hostile negotiator *faxed* a copy/version of their approval letter to my realtor. His version of the letter contained the following sentence/language about the ~$50,000 deficiency difference:
"Any deficiency balance remaining on the loan secured by the
above-referenced property will be waived". I lived in bliss for a
week, thinking my long nightmare was finally over.

Seemingly at the same time, Chase *mailed* to my house via regular first class mail (arrived 1 week later) an
almost-identical letter, with the same date in the text (though USPS postmarked it the following business day), with one *key* difference, the above sentence about the deficiency in this letter was replaced by this: "Nothing contained in this instruction letter shall be deemed a
waiver by the lender of any deficiency balance". Both versions of the letter ask me to
sign and return (via fax) the "original" (i.e. mailed?) version of the 'Borrower Acknowledgment form" that accompanied the letter. One other important difference in the two versions--the mailed letter has the front/odd pages printed with bar codes, and there is some sort of sorting/database code above the property address on the first page, both missing from the faxed version. This makes the mailed letter look slightly more official to me.

My belief is that this was a deceptive, intentional "bait and switch" tactic aimed at tricking me into returning a signed Borrower Acknowledgment form that they can claim acknowledged the second version, then after closing Chase will contend that the faxed version was a mistake and the mailed version was the "official" version, and debt collectors will be able to pursue me indefinitely for
the deficiency, since that version says they can legally do so. My guess is they were thinking if they were caught and had to change course, Chase can claim it was a simple mistake.

Obviously, I am not proceeding to closing with the "nothing contained" letter not being corrected/retracted. I am waiting to hear back from short sale lawyer and the constituent services staffer for my member of Congress; I'm hoping having both of them contact Chase will scare them straight and I'm asking that Chase re-mails an "official looking" version (with barcodes) with the zero-deficiency language.

I welcome your thoughts and suggestions on how best to proceed if anyone else has experienced this. It also struck me that this might make for a compelling story for the news media. Seems like calls from reporters might also have a desirable effect. Has anyone successfully put media pressure on their lenders? Finally, is it even worth my time or helpful to file a complaint with the State of Florida Division of Consumer Services?

Thanks and good luck to you all.