Ironically two people mentioned tonight that they made the chocolate chip cookies recipe that I posted. And both commented that their cookies came out flat. The only reason I can think that they'd be different is the altitude and humidity. We have no humidity here, so that could be the problem. Shortening makes cookies cakey-er =), so I would try using half shortening, half butter. If you like the butter flavor, Crisco makes butter flavored shortening.
Let me know if you make them again and if this helps!