I agree with Little about documenting things and playing by the rules of CYA, of which documenting can become a HUGE part, I would be very careful about "opening the door" to harrassment. Someone may consider what you are doing, "exposing yourself" (obviously many of us think this is absurd, but we don't work there) is harrassing to them... A jealous co-worker as an example.

So try not to let this thing get blown up. Be "thankful" that you received a warning and not a written reprimand and just pay a little closer attention to the clothes you wear, how they fit and what gets exposed when you bend down or bend over or whatever.

If you ever receive anything in writing from anyone other than HR, like an e-mail from a boss or co-worker, print off a copy and TKAE IT HOME with you. Keep a file of everything you receive that you deem "inappropriate" from anyone. The more of a paper trail you can build the better off you or anyone else will be should the need ever arise.