Another profile evaluation :)

Hello,

I would definitely recommend taking the GMAT again. Almost all of those things are in your past and can't be changed: your undergraduate transcript, your work experience, your community involvement, etc. Assuming you will apply soon, from today going forward, the only things you still control are: your GMAT score, your essays, your letters of recommendation, maybe additional college coursework, and your admissions interview.

How you present all of those backward-looking things will significantly impact your chances (and that's what our MBA admissions consultants do), but what would you rather do -- submit a 640 along with a terrific optional essay explaining that you really can cut it at Columbia/Kellogg/INSEAD, or a 700 with no explanation needed? Very few applicants are perfect, and admissions officers accept applicants with blemishes all the time, but why have that one additional blemish (or, at least, something that's not a strength) on your application when you still have a chance to improve on it?

Beyond that, I wonder about your extracurricular activities and leadership experiences at work. Since you didn't mention them here, I worry that maybe you don't have much in this area. But, if you do, that will probably be the difference between not being competitive at these programs or having a decent shot at them.

Good luck!
Scott