I renewed my FCT this morning and started a download. When the download first starts the speed are way over 1 Mbps, however it quickly slows down to 6 Kbps.
You may not need to reinstall it. Inside the <trainz install folder>/Bin folder, there is a Jetlog.txt file. If you can, open the file and paste the contents.
I found that there was a SW engine open for edit that I was not allowed to commit. I reverted it, and then I could launch Trainz, however I haven't played in a long time and noted that after starting trainz, I had to right click the icon in the tray and choose Trainz again for it to launch.