Don't be too down on yourself. 640 is not a bad score at all.
1) What schools are you aiming for?
2) Are the programs F/T or P/T? The latter, in general, have lower mean GMAT scores than do F/T programs.
Taking the positive from this, your quant. score is great! If you have MS Access loaded on your PC, one tool that I think can help your verbals skills is located here - http://www.gmatclub.com/phpbb/viewtopic.php?t=15919
. Use the database to focus on the verbal sections that gave you problems - start with the easy questions and work your way up to the difficult ones. BTW - the database references questions in the OC 10th edition.
Good luck and don't give up. With an improved verbal score, your GMAT score will easily be in the 700's.