[ by Melanie Gretchen ] MF Global trustee James Giddens, who's responsible for liquidating the bankrupt firm's brokerage arm, is having "substantive discussions" with JPMorgan Chase about claims filed against the bank.  JPMorgan was one of MF Global's key bankers, especially during the final days leading up to MF Global's collapse on 10/31/11.  That role has placed JPMorgan into the center of the controversy which, in turn, has drawn scrutiny and claims from investors around the world. Trustee trustee James Giddens says JPMorgan has cooperated with his office's investigation, provided staff for witness interviews, and assisted in reviews of documents by trustee lawyers and accountants from Ernst & Young.  Yet, when it comes to defining "substantive," as in talks with the bank, it is a mystery and still anyone's guess as to where the 2 sides are with regard to a settlement.  They can be close or far apart because "substantive talks" could mean anything. Ultimately, Mr. Giddens has the option to sue the bank and others to try to reclaim assets, if he determines that such other parties should not have accepted money from MF Global in the days prior to its bankruptcy, a person familiar with the matter said in recent weeks.  JPMorgan officials continue to insist the bank did nothing wrong in the case.  [WSJ, 4/6/12]