In Reply To:
Most likely an undersized seatpost. A few recent references to it in this thread. Your LBS should have no problem getting a remedy from our warranty and tech services troops.
I got my SC7 last week and on my first ride I was about 20 miles out and my seat slipped down to the top tube. Took the bike to my LBS and they are working with Trek and taking care of it. I am confident it will be fixed within a week or so, what ever the solution may be.
BTW, the bike (SC7) is ridiculously comfortable, smooth, positive shifting, predictable and stupid fast. When it get it back from the shop, I will snap some pics and post them on ST.
Trek 1500 SLR Road
Trek SC7 Triathlon