Hi - I just took the GMAT for a second time and scored the following:

700 - Q 66%, V 95%

This is an improvement from my first time taking the test:

640 - Q 63%, V 82%

I want to attend a top 20 school. I am happy with my improvement as I was aiming for a 700, which I believe will round out my application and make me competitive for these schools, but I am concerned about my low quant score, especially since I don't have much of a quant background (one calculus class in college, got a B+). I plan to get my MBA to continue a marketing career. On the MGMAT and GMAC practice tests I was scoring in the high 70 - low 80% in quant, so I am not totally deficient in math...

Will the schools see this quant score as a big problem?

It really depends on the school. You can contact the schools to which you want to apply and ask them whether they consider the individual subscores or only the overall scores. I have also had some students with "light math" backgrounds take an accounting or calculus course at a local college to show more recent quant work - but, if you do this, you MUST get an A in the class. Don't do that if you're not going to work your tail off and get a great grade!

Also, post this same question over in the admissions consulting thread to get the opinion of the experts over there. (If you know which schools, too, mention the actual names - the admissions consultants know what a lot of the schools really want.)