Last night I completed a flight from La Guardia, NY, to Cleveland, OH, (KLGA to KCLE), flying the US Air 757, and did an auto landing on RWY 24L, which was successful.  I had to go around on the first try because I had selected the wrong ILS frequency on the NAV radio, but the second attempt worked.  I set up the IRS, which took quite awhile to respond correctly.  Whether this is necessary I am not sure.  There is good documentation in the CS-757 manual, Part 2, on using the IRS to allow the normal operational mode of the NAV mode, which may be helpful.  There are also two tutorial flights for the 757.  The CS-757 is a great aircraft, and I hope you can get the autopilot issue resolved.

Jim Kaye