If you are receiving constant database errors, then there's something wrong somewhere. It could be a failing hard drive or memory which is causing data corruption, or it could be just plain corrupted data in your Trainz install. I highly suggest you back stuff up and attempt another repair. The constant repairs could also be self-inflicted by not letting Trainz shutdown completely before turning the computer off, or allowing the machine to hibernate while Trainz is running, which I have found causes problems.
Do not start Trainz to initiate a repair. Instead perform your Quick Database repair in Content Manager. The repair process may take a very long time so plan on doing something else. Perhaps even start the repair when you go to bed so it has a chance to run overnight unimpeded. When the repair is completed, check in Content Manager for faulty content. There will be some items listed. Highlight these items and view errors and warnings. These should disappear from the list. Any remaining faulty assets can then be repaired or downloaded using the normal methods. In the event that something cannot be repaired, the only option is to replace the asset from backups or redownload.
Once the database has been repaired, do not close Content Manager. Also do not start Trainz immedaitely as the database will now be validating assets. This process to can take some time, and cause the program to display a not-responding when attempting to access anything on the route menu or other functions withing Trainz.
Once this is complete, depending upon how long it took, you can then use Trainz normally.
If you continue to receive errors and updating database messages, then you need to investigate further as this could be faulty hardware causing this problem.
John