Unfortunately, you may need to re-install Trainz 2010 - due to the way patches work, the system needs to be on and working throughout the whole patch installation process otherwise one or more files can become corrupt/not matching the information required for the patch to work. (Also, there is a higher chance of Trainz causing fatal errors or even not loading at all if your system died before the 'Updating Trainz Database' stage)
I apologise if this is not what you were hoping for, but I've had failed patches before and had to re-install the program concerned.
Shane