anything is possible
so far, in all that i have read, they are not able to link insecticides to CCD. there seem to be a number of things that argue against it. among them, the fact that this is something that has happened before.
there were just a couple of articles posted here about a nosema. as i recall, researchers in spain and other places identified it as a likely culprit. it's probably posted close to this thread. one or two back.
that said, i can't imagine that insecticide is really good for bees....but neither is having your crops eaten up by other insects.....