Current version of osrmt doesn't suport installing on 64bit systems. To solve:
1) Download the latest izpack.jar file
2) Extract the native/ShellLink_x64.dll and rename to ShellLink.dll
3) Overwrite the existing osrmt.jar/native/ShellLink.dll with this new one. (FWIW, I also copied COIOSHelper.dll into that directory, not sure if it's required)
Presto, a 64-bit installer.
I cannot find a /native/ folder in the download for Version 1.5. Does this version fix a 64-bit install? I am getting just a flash of the Command Monitor (Windows) menu and then there is no opening of the OSRMT client. Also, the install does not add an icon for OSRMT anywhere that I can find. All I see is the OSRMT folder in the Start menu and it gives the behavior mentioned above when I left click on OSRMT Client.
This method did work. you could open the osrmt.jar by Winrar, and replace the ShellLink.dll by one from izpack.jar. If you could not find ShellLink.dll from izpack.jar, please install izpack and you can find it in installed directory.