I have the same problem with my KUbuntu going to sleep in 10 or so minutes even though I have the power management settings set to hours. There was a flash update that failed the other night (and I haven't had the time to see why or fix it.) Try to first check for updates, make sure they don't fail. If that doesn't work, I'm probably going to give up and just try a different distribution.
OP - if your users are anything like my users, nothing will ever be good enough and they abhor any changes whatsoever. Try to pick the path of least resistance (for you), which may very well be new hardware with winders. Also know that no matter what, you'll have a month of hell (your hell - also depending on number of users) for most of the users and a small subset of users will always be unhappy with it, think it is the computer's problem, think the computer "hates them" and not be able to do their job no matter what. That is when you have to be an ass and put your foot down and tell your boss to tell their boss to tell them shape up or ship out. Don't tell them yourself, then they get all pissy that you are pissy and that never turns out well.