Hi,
Rather than speculate, you should give the school a call. My experience with admissions is that they are generally happy to discuss your profile and give you an idea if you may be a fit for their program. Admissions depends on the person as a whole, so if your 10 years of experience would bring an important perspective to the program, they may be fine with your score.
A 640 is really not so bad, and you can go to many good programs. It depends on what you want to do. If you have your sites set on a top 20 program, you most likely need to retake the exam. However, if you're looking at some strong regional schools that will give you what you need to go to the next level in your career, it may be just fine. Check out a publication like US News and World Report's annual MBA guide, because then you can see avg GMAT score of each school's incoming class. This will help you know your options.
Best wishes,
Tatiana
Tatiana Becker | GMAT Instructor | Veritas Prep