I dont suggest GMAT club challenges
during last 2-3 weeks to your test. Rather concentrate on brushing up your concepts. Challenges are difficult and can really shatter your confidence. It took me almost a month to come to terms with challenges. I started off with a dismal 31 percentile and then after a montho r so i started hitting 75-80 percentile consistently.
skaballet: to go from 41 to 45+ you dont require challenges IMHO. You should concentrate on learning the basics again. Do practice sets from OG and other prep material. Once you are comfortable with all these books then come to challenges. Just my 2 cents.