Blinking screen

[S D Law]

We have a Sun 3/60 running as a server.  When one of our users (at the
console) runs her C graphics programs (using GKS and sunview tools) the
graphics window starts to blink consistently.  It doesn't happen to normal
sunview text windows and it doesn't happen on the client Suns.  All TeX
windows have a similar effect (Could this be because TeX uses the same
device as the graphics windows) as does lockscreen.  If I reboot it stops
for a while but does come back.  Anyone any ideas whats causing it as its
becoming annoying.