Replying to How to get the best audio recording out of dslr

For the past year I have been running my rode video mic pro straight into my camera when recording audio. Most of the while it seems to work really well but as of lately I have been getting a lot of static when recording people talking. I have a somewhat large shoot coming up this week and would like to know the best way I can get clear, crisp audio. I currently have ML on my camera and also make sure my audio never clips and also that my automatic gain is never on. My question is why do I get static in my recordings when it appears that there shouldn't be any with ML. (I have also fallen into a pretty nice deal that may be able to yield a 5d2 so if you know anything about audio with that camera it could be helpful.)

As far as external audio recorders go, I have played around with a Tascam (the twin of the zoom h4n), but still had noise when I used that too. For a long time I have been considering a H4N or a pre-amp but would it really be worth it? I have finally started to receive a somewhat steady flow of money from "commercial" video work so I am willing to invest some money that will give me clean, clear, and crisp audio recording. Right now I have been scrapping by by removing as much of the noise as I can in post and having a song that can cover it up.

Thank you all ahead of time for your help!