A bit late coming to this party, but running Trainz on multiple computers can cause a problem totally caused by the user (I know from experience)! In my scenario, I have all my Routes/Sessions on my latest PC, but the original/earlier copies remained on my "retired" PC however, its retirement did not last long. I started to use the "retired" pc to play trains on my earlier routes which dictated making modifications as I saw necessary. I also experimented with landscaping techniques, and even started new Route ideas on it. My main PC was being used for working on existing new projects ..... and you can probably see where this is going! The 2 pcs were stating to get "out of synch" so I decided to correct the situation and imported all the Routes/Sessions from the retired PC. My thinking was that I need to focus totally on the new PC (a self-discipline issue). The end result was that I lost a couple of Routes in progress because of (I believe) a duplicate kuid numbering issue. Of course I had backups, but I used to back up my kuid number so I could not simply reinstal a specific Route/Session. After going through a sequence of 149790 installs on the "retired" pc, I did manage to cut my losses to a single Route ...... but the whole exercise was total frustration with my own lack of foresight, discipline ......... whatever! You have been warned!!!!!!!!!!!! Regards. Colin.