If you’re having problems with your Undo Levels being reset to zer0, it could be a C++ plugin that’s doing it (or less likely, a NetView page). C++ plugins (and NetView pages) that set the Undo Levels to 0 and then don’t restore it, either by oversight or because of a crash/error, can leave you with your Undo Levels set to 0.
In constrast, we prevent scripts and script-based plugins from changing the Undo Level permanently: as soon as the script finishes execution, Softimage resets the General.undo preference to its default value.
For example, if you run this in the script editor:
Application.SetValue("preferences.General.undo", 0, "")
You’ll see this logged in the script history:
# VERBOSE : Restoring preference changed by script: General.undo
eX-SI 
I’m not sure if i’m doing it wrong but it doesn’t work for me. I tried running it using SI 2013 with VBScript, JScript and Python.
What’s not working? You don’t see the message logged?
You may not have Verbose logging enabled (by default, verbose is disabled).