Yep! this game can be a real bitch at times but we still keep coming back for more pain.
It looks like you will have to redownload the game, but one thing I would like to ask first is, What did trainzdiag.exe say when it finished installing? did the diagnostics give your computer a clean bill of health with a full row of ticks? if you need to run this again you will find it in the Bin folder of TS10 just click on trainzdiag.exe, if it comes up with a problem, post it on here.