Xset issue

I am having a problem controlling my DPMS settings. This is on
a SUSE 7.3 box, running the default kernel, XFree, with icewm.
Currently, the box turns off the monitor after about a minute.
I need to change that to one hour. I've tried using:

xset dpms 3600 4200 4800

both as root and as my unpriv user, and it still turns off the
monitor after about one minute. I tried:

xset -dpms

as root to turn off DMPS completely, and the monitor still turns off
after one minute.

What am I missing?

George