Hello,I've tried searching here but found nothing. For the second time now it has happened to me that my FMC gets errouneous heading from FS. You notice it by watching the compass swing back and forth as LNAV tries to correct. When I press shift-Z I see the heading changes as well, meaning that for some strange reason, FS keeps changing headings. LNAV of course is unable to keep track of the route, you get frustrated and you eventually abandon your whole flight.Not sure yet, but it seems that when I press slew, the heading reverts to what appears to be the correct value. Release slew again and it appears to want to drift again. Any idea what this might be?Thanks,XanderDell Dimension 9500Vista 32FS9PMDG 747AS6FSInn

Xander is this the only simulation model that this occurs with? Just trying to work out if it is n FS9 issue or the PMDG 747.I see you also run Vista. Did it do this with XP?