I'm going to make a guess here and say that Stevevista is using a screensaver
set to 10 minutes, and that someone ticked the "On resume, display logon
screen" box on it. Another somewhat less likely possibility is that "Require
a password on wakeup" has been set in the system's power settings and that it
is going into standby or hibernation every 10 minutes.
If it's the screensaver, just uncheck the box. If it's the Power Setting
issue, then tell Windows to NOT require a password at wakeup, or tell the
system to wait longer before going into standby / hibernation.