How long have you been running the a/c since your reset? It's possible that the ECU just hasn't relearned the idle speed properly, thus can't adjust when the compressor kicks in. Take it to a dealer and have them plug in to reteach the idle. If that doesn't work, it could be something mechanical with your compressor, or possibly just a bad belt. I'm shooting in the dark but I think I at least sound like I think I know what I'm talking about.