Mixing up 2 subjects
Dont confuse sexual harrassment with flirting, although in today's PC world that line is getting more blurry.
Generally speaking, never date someone who works for you... directly or indirectly. If at some point her place on the org chart connects to yours, you are in a position of influence, and in a "he said, she said" debate, you automatically lose. Don't do it.
Dating someone in a separate division or part of your company is less clear. Within the workplace, do not mix personal and business, and if you cant distinguish the two, don't do it. If you are one of the rare few who can keep the two worlds from clashing, go ahead but be discrete.
As for flirting... the farther up the ladder you are, the farther you have to fall... and the bigger the target you become. The gold diggers and game players go for the biggest prize, so if you are in that position, be skeptical of any sort of suggestive comments. The best advice is to string her along until she makes the first overt move and keep control (as Seinfeld put it... make sure you have "hand").
And remember, we're talking about worst case scenario and the minority of women... most instances are indeed harmless flirting and banter, but make sure that you know where that line is.