Just purchased the 757-200 and am finding problems with the AP.  I'm used to flying the another company 767 and expect that the 757 is fairly similar.  I've studied the manual and looked at a few of the tutorials on the site and am pretty sure that the IRS and FMC are set up ok.
Problem is that that when I takeoff and switch Lnav and Vnav on, followed by the autopilot, I dont get any lateral nav and soon overspeed - the autothrottle doesn't seem to work.  Vnav will capture a set altitude and switch to hold mode ok.  If I switch Lnav off and use the heading select knob, the autopilot doesn't follow.

I'm running Winxp with FSX SP2 and FSUIPC4.6 (have also tried the 4.5 which comes with the 757).  All other aircraft fly ok on my system and I've reinstalled CS757 just in to be sure.

Got me well puzzled and not sure where to go from here, hopefully I'm just being dumb, next stop technical support I guess.  Any ideas appreciated.

Gerard