Again a VBScript problem.
Here is a working code
Set WshShell = WScript.CreateObject(\"WScript.Shell\")
WshShell.Run \"\"\"C:\\Program Files\\TrueCrypt\
Instead of using the Shell Run method you could try the Create method of the WMI Win32_Process provider.
The example on this MSDN page creates a configuration object to set the process option ShowWindow to SW_NORMAL (i.e. 1) for a GUI executable - NOTEPAD.EXE.
On this page it looks like SW_HIDE (with a value of 0) is also an option.