Is this bike brand new, or did you get it used? The reason I ask is that you could have a worn chain on a new chainring (or vice versa), which will produce bizarre shifting problems, which often times won't show up unless you're pedalling fairly hard. i.e., repair stand it'll work fine, out on the road, it won't.
How fast / hard are you pedalling when you go to shift? You do need to be pedalling at a reasonable cadence, and it can help to "lighten up" a touch when you shift. i.e., if you're straining to turn the pedals, it is way too late to expect a "clean" shift.
You can encounter some bizarre shifting issues if the frame itself isn't aligned properly, or if the various components of the drive train aren't fully tight (although loose drive-train components usually reveal themselves in a variety of creaking sounds). Determining frame alignment requires some funky tools, but any shop should have them. If your frame is bent, it's a warranty issue and Cannondale should just give you a new bike.
If you're mechanically inclined, check out
http://www.parktool.com/repair/readhowto.asp?id=75 for a very comprehensive guide in adjust your front derailleur.