I'm plaegerizing here, with apologies to Lonewolfdon.. But this is some pretty good advice.. Hope it helps..
Does the same problem occur for all scenarios, or just one or some?
Some things you might try;
* Have your Steam-Client and the RailWorks executables are set to run with Admin level Privileges with Windows.
* Have permissions set with any firewall to allow Steam-Client and RailWorks.
* Have your Drivers for Graphics & Sound, DirectX, PhysX, NET Framework and Windows all up-to-date. Sometimes a driver or Windows component can become corrupt and may need to be re-installed / repaired.
* Do a full scan of your computer for any viruses / malware that could be lurking.
* Close any unnecessary programs before launching RailWorks.
* If the problems still persist, you might consider trying to contact official RailWorks Support;
http://www.railsimulator.com/support.php