just trying to help...
Sorry to learn of your problem; I'm probably not qualified to troubleshoot it, but here's a bit of friendly advice:
I think you'll be more likely to get some help quickly if you post this request in the right place on the Forums. The guidelines for this section (General Trainz) indicate that "All requests for technical support should be posted in the relevant area in the Maintenance of Way forums."
Also, it might be easier for some one with more experience to provide an intelligent response if you indicate what version of Trainz you have, and it wouldn't hurt to know what OS (XP, Vista, etc.) and video card you're using, too.
So, you might try providing some of that information in a new note posted in the appropriate Maintenance of Way area.
Good luck with your weird problem!