Agree – Do some squats and dead lifts, and cleans – these will increase your body’s capacity to respond well to plyos and other jumping programs.
A running jump over 45″ is not that great, but if you are just trying to boost your vertical for dunking or whatever, then I wouldn’t be too concerned about what you can jump over 🙂
The other thing that will help you jump higher?? Just plain jumping. When I was really into working on my vertical jump – 2-3 times per week, I would get really warmed up and then do a series of 1 and 2 footed jumps as high as I could go. Maybe 10 jumps off each leg and 10 off 2 legs – trying to jump a little higher each week than the previous.