I just developed a very similar problem on a new 2005 Lemond Poprad (~450mi)

The tapping/ticking comes from the wheel, most likely the rear, but it is very hard to tell. It is only sounding when I am on the bike riding, even when coasting. I can not duplicate on the stand, it seems the wheel needs a load to produce the sound.

I am very certain it is not:
-wheel hitting rubbing anything, brakes, etc.
-debris in tire or tread problem
-chainline related

I checked the spokes and they are seem to all ping the same tone, none seem loose. But right now that remains the primary suspect. I don't have the experience to know how to find what spoke to check.

I listed to the front and rear bearings (put one end of rod on the wheel axle and the other end against ear). The front is like butter. The rear had a bit of roughness in sound, but no repetetive noise.

I'd like to take it back to the LBS where I bought it, but right now need it every day for commuting, so its going to be a while. The tap, tap, tap noise when riding is getting quite irritating.

Al