Getting a 30 day deliquence notice (original creditor) removed after creditor refuses

[masonuc]

Here's my situation. I have good credit and have used it buy several investment properties. I am looking to buy a few more but need a middle score of 720 and my credit score has dropped slightly below that thanks to a problem with a bank. I had a $50k line of credit with them. In April 2009, I borrowed the full $50k for a short time and because of a problem on their end (they had deactivated automatic payments), I missed the first payment due on the line that month. It was about 45 days late. I paid off the entire amount a few months later and the account is still active but at $0 balance. I have tried calling the bank to have the 30 day deliquence from April 2009 removed (they reported to all 3 bureaus) and gotten nowhere. All I got was a form letter saying they can't remove it. This is the primary factor keeping my credit score below 720. It is costing me at least 20-30 points, maybe more. I have no other deliquencies on my report.

Any ideas on how to get this removed quickly? If it matters, the bank is Suntrust. I realize this will diminish in effect in several months, and go off completely in a few years -- but I need a quick resolution or I may miss out on a good opportunity available now.