I loaded Solaris 9 on a Sun Ultra5 (fresh install), 3 hours later the
installation was finished. So I rebooted and logged in. Everything
looked fine, but after 2 or 3 minutes the display (except for the
window I was working in) went black. 30 seconds later, the window I
was working in went black too.

I hit the power switch in front. A window poped up asking if I wanted
to shutdown. I clicked yes. After it powered itself off, I powered the
machine on, logged in again, went into window properties and disabled
the screen saver/blanker and power management, but the same thing
happened again. I put the monitor on another box, no problems there,
it's not the monitor.

Any thoughts?