This means that your PATH is not defined correctly.
Any NX command line application should be launched from a NX Command Prompt to ensure that the environment is set up correctly. Use Start, All Programs, Siemens NX##, Tools, Command Prompt to open a NX command prompt.
If you are writing batch scripts, you need to be sure to set up the environment properly by calling ugiicmd.bat properly first. Examine the properties for the start menu shortcut referenced above for syntax: