737 gurus, please:I have not changed loads, nor have I fiddled 'much' with the PERF settings other than load. I've varied the GTW load based on distance, but I'm missing something.My problem is that using VNAV and LNAV (as I usually do), both the 800 & 900 have trouble maintaing a cruise speed over .60/200K give or take a lie. I have to resort to manual speed control to get any airspeed, eg. about 280K at 350. And yes, I use the fuel calculator to determine fuel load.Any ideas what I may have input incorrectly?

Ron,-Do you have the Autothrottle armed?-Check the CRZ page in the FMC and see what speed entered is. Should be ~M.79

>Ron,>>-Do you have the Autothrottle armed?>>-Check the CRZ page in the FMC and see what speed entered is. >Should be ~M.79Also, if you just upgraded to FSUIPC 3.51, there is a major problem with the way it handles winds. Peter's got fixes in beta test now, but you can get major MAJOR deviations on climb and descent. Go back to 3.50 for now.

Thanks guys... ;-)A/T is set, but I'll have to check the cruise page, and FSUIPC to see if v351 is the headache.