Flashing Dell FP monitor

["John Fleming" <john@wa9als.com>]

Debian testing - Using a new Dell FP monitor, I have the following problem -
Using the KDE desktop, it is fine for an hour or so.  Then the display will
blank whenever the screen updates with a new window etc.  Then after another
hour or so, the whole screen will start flashing every few seconds even if
left unattended.  If I shut off the monitor, it will start the cycle again
the following day when turned on - OK for awhile, then flash with window
changes, then flashing regularly even if unattended - unusable at this
point!

If I use the monitor with a Windows computer, it doesn't do this.  If I plug
a CRT into the Linux box, it is also well-behaved.  It's the flat panel with
the Linux box combination that's problematic.

Any ideas about this?  It seems very strange to me that it takes awhile
before it acts up.

Thanks - John