First of all which trainz are you running? But it could be if you have TRS2006, then it could be becuase you installed SP1 but not thew right way,or it was a faulty install.So you have to uninstall trainz,reinstall,then install SP1. But if you have any custom content,then first make a copy of the local folder which is in all Programs.... then once you reinstall everything go into CMP and go to import content and find the place you saved your copy of the local folder.