Well, let's see if the problem is reproducable.  I have flown four plans, the first four from World's 100 Busiest Airports.  Sao Paolo Brazil to Santa Cruz, Colubia, then to Bogota, then to Mexico City and from there to Houston.  Some have included some fairly complicated procedures, including holds, and conditional fixes, e.g. fly runway heading to 9200' then turn.

I have not had one problem with the FMC doing anything but exactly what is supposed to do.  In fact, it seems particularly convenient, functional and robust to me.  So all I'm saying is that in a variety of routes in two hemispheres, the FMC is a solid part of at least the version I got.

If you provide a complete route that you have been unable to fly successfully, I would be happy to try it out.

I am using the latest Navigraph data.

There are just too many weird problems being reported that don't make any sense.  Al Bradbury over at Avsim reported he was having problems until he did an uninstall and fresh reinstall of FSX.  I'm not advocating anything so drastic here, but I don't see how it can be a problem with the airplane if it works find for some people.

So if someone wants to shoot me a (preferably shorter) route, let me see what happens.

ADDITIONAL:  The FMC is pretty complicated.  It does a lot.  If you are creating routes in another program and importing to FSX, then importing that to your FMC... I notice that there are some routes that work with SIDs and STARs, and some that (realistically) sort of leave you hanging because they are going to vector you.  I also notice that you might have to work with a route, with a STAR, to get it the way you want it.

For example, I just planned KIAH to KMIA.  On the procedure chart and in the FMC both, the SID just starts several miles from the airport.  That means you are to expect them to tell you how to get there, I believe.  Other charts will actually show you turn here, pick up that radial, whatever, all the way from the runway, but this one doesn't and we must live with that.

And at the other end of the route, both the chart and the STAR in the FMC kind of dump me without a route to a particular runway.  Again, I'm expected to get vectors.  I think realistically, some airports are just that way.  I made a route myself that will take me right to the runway where I can pick up the localizer, based on the approach plate for 8R, but that isn't exactly realistic for this particular airport, I believe.  In other words, I created a made-up STAR to avoid messing with ATC (because this is FSX and I can!)

For my alternate route, everything is the same, expect it follows the real procedure, which dumps me and makes me follow ATC.  In both I've added altitude and speed restrictions, and multpile holds, just to see what happens.

I think sometimes you can do a route dump from FSX with not problem.  Other times you are going to run into challenges that aren't necessarily unrealistic.  When you are starting from another program to begin with, I don't know.  I'm just thinking out loud here, and will fly this route tomorrow, since I have to get up to go to work in about five hours.

But I've been thinking, Mr. Schmid, and if your engines are stuck at 300 kts like you report, you obviously have something FUBAR with your installation.  I wouldn't expect the FMC to work.

I am beginning to think that we are seeing trouble reports from people who have installation problems and/or operator error.  I have been studying this airplane intensely for several days (I have to) and I am still learning a lot.  This is a self-selected group and it is impossible to make a judgment on the product.  IF even one person is getting it to work right here, that tells me we can't just say the FMC doesn't work.

If the FMC turns out to be garbage, I'll be the first to say so.  However, I respectfully submit that we owe to ourselves to not be premature about this.