PMDG 737 FMC Not Working

Hi All..
My FMC on the PMDG Boeing 737 has stopped flying its pre determined
course after working fine since I installed it.
It allows me to input all of the data for my flight...Waypoints, SIDS
STARS etc. but then if I try to set the course and heading to that of
the departure runway it doesn't seem to orientate itself (i.e. straight
up as if I am heading directly North like it used to)
Worst still, when I take off and engage LNAV & VNAV the FMC displays
that it is flying towards the next waypoint of the previously inputted
flightplan via the FMC but deviates away from its pre plotted course.
If it tries to execute a SID (DP) it swings left and right and the
triangle that depicts the aircrafts' present position gradually moves
away from the purple pre defined FMC routing.
The next waypoint gets further away not closer !! I have the last
"Free" NAVDATA AIRAC installed if that means anything.
Any ideas out there to stop me pulling my hair out??

"Pete" <piperwarrior5 DeleteThis @hotmail.com> wrote in message
news:1164142267.559306.271200@j44g2000cwa.googlegroups.com...
> Hi All..
> My FMC on the PMDG Boeing 737 has stopped flying its pre determined
> course after working fine since I installed it.

Something has changed, then. Have you made any changes that might affect
this?

> It allows me to input all of the data for my flight...Waypoints, SIDS
> STARS etc. but then if I try to set the course and heading to that of
> the departure runway it doesn't seem to orientate itself (i.e. straight
> up as if I am heading directly North like it used to)

Not too sure what you mean by this. The orientation of the aircraft symbol
when in 'plan' view depends on where you are positioned when you set the
heading and course. It will only move when your aircraft moves, not when you
input heading and course. The same applies to the triangle in 'map' view. I
assume that you have entered the departure runway into the FMC?

> Worst still, when I take off and engage LNAV & VNAV the FMC displays
> that it is flying towards the next waypoint of the previously inputted
> flightplan via the FMC but deviates away from its pre plotted course.
> If it tries to execute a SID (DP) it swings left and right and the
> triangle that depicts the aircrafts' present position gradually moves
> away from the purple pre defined FMC routing.
> The next waypoint gets further away not closer !! I have the last
> "Free" NAVDATA AIRAC installed if that means anything.
> Any ideas out there to stop me pulling my hair out??

You say the FMC indicates that it is proceeding to the next waypoint, yet
from what you say, it is behaving as if a previous waypoint has been missed
and it is trying to locate it. Without seeing what you are doing when
inputting the flight plan it is difficult to be sure of what is happening.
Why not visit the PMDG forum over at Avsim. Someone there may have
experienced what you describe but certainly one of the PMDG guys will be
able to nail it, I'm sure. Good luck!

Iain