Can you be more specific with regard to the nature of the unreliability? Is it not working at all, or is the problem sporadic?
One quick thing to check (from personal experience)...
Has the user configured the "What to do when I come back" to "Set my status to what it was auto-changed from"? If so, do they also have Windows power settings set to turn off the monitor?
If the answer to both of these is "yes", then this may be your problem. When the screen is turned off, Windows can report to applications the the Screen Saver has ended (since, technically, it has) which is interpreted by Desktop to mean it's time to revert the status. If you change the setting to "Set my status to" and use the same status as you are using for away (e.g. "Away from Desk") then that might sort it out for you.
HTH