Thanks guys. I keep thinking that it's the CV too. I've been under the VX and everything drive shaft related seems fine. No slop in the U-joints, the drive shaft doesn't move when I try to rotate it, and I've lubed up all three of the zerk fittings on the rear shaft.

Under normal driving conditions the CV doesn't make a clicking sound, BUT I did put it in 4 low and goosed the throttle a little and did get the tell tale clicking. The mechanics explanation for the noise at highway speed is that maybe the inner CV is shot and has been wallowed out by all of the yuck that has gotten into it, so that the CV "locks" into place out of round and the vibration/noise we are hearing is the front half shaft spinning out of round.

Still haven't heard back from the mechanics yet (they're getting a call RIGHT NOW) so I'll let you know what I hear in case this happens to somebody else.