here's my thought, for what its worth. when i couldn't get cmp to close so i could launch trainz (2006) i'd do a system reboot. that would shut down what cmp was trying to do but couldn't (namely auto-update itself over the internet, which it couldn't for reasons unique to my system)
also i would always ftp download my cdp's whether from dls or wherever else.
then under the file menu in cmp, inport cdp and then commit.
after i'd commited all my newly downloaded cdp's, before attempting to do ANYTHING else, reboot the os.
not that difficult and only takes a few minuets.
THEN launch trainz to survey, drive, see if the new stuff, if its rolling stock, came in in train yard, et al.
(not showing up means not having all the parts. sometimes simple to solve, sometimes something of a huntin expedition)
but i think the main thing, ok, from the launcher, or anywhere else, only cmp OR surveyor/driver/trainyard will run. not both simultaniously. i think the confusion is maybe the launcher looks like trains is running or something. no. that's only the launcher. then whatever you click on from it, only that one part will actual launch and run.
as pointed out, in principle you are supposed to be able to move from one to the other and back again, but only one at a time is actually running.
and like i said, cmp 2006, especially without sp-1, has a problem, its auto-update download, with relinquishing control of the system, which, the way i found to turn off cmp, and regain control so i could run surveyor/driver of the rest of my NONE trainz related aps, is to reboot.
otherwise, cmp keeps trying to keep running and keep atleast partial control. rebooting is the one, just about foolproof way to turn this off.