I followed the advice and even though i don't know what solved it, I didn't have that error for a while now, it's a blessing.

The most likely cause was a "move to" order to an empty (but existent) TG (Shipyard TG) that was in one of the repeated orders

Try clearing all the civilian shipping lines orders, if clearing all your own task forces doesn't work.

well, i can't speak specificially for this error, because it pops up occasionally.  As you get more and more comfortable with how the game actually works, you realize there is a lot of potential for users to create errors.  For example, I had errors and crashes one day because I had set an infinite loop of orders-- move to earth/refuel from earth... for infinity.  Before I knew the basic way to play the game, I broke it badly and had to start over.  When it gets stable, check all of your task groups for strange or impossible orders, like unloading goods that don't exist from a colony that doesn't exist.  Sometimes, these problems happen within NPR systems, and then there is not much recourse.

I now play with NPRs off at start, and deal with them as I encounter them.  It seems to cut down on the disasters.

Search the forum for the SPECIFIC error, and post the entire message and someone might have a better idea whats going on.  But things break occasionally.  If it can be isolated to an NPR, maybe SM-Deleting the NPR would help.