Bug#529178:

[Chris Bainbridge]

The Dell 2209WA had some DVI hardware glitch that caused these mysterious
blackouts.

See extended discussion:
http://en.community.dell.com/support-forums/peripherals/f/3529/t/19257125

And upstream: https://bugs.freedesktop.org/show_bug.cgi?id=89110

Some users reported that Sapphire fixed the problem with a BIOS update but
for other manufacturers it was always an issue. Using an active DisplayPort
adaptor was the recommended workaround in the end.

Final comment from Dell:

"Posted by DELL-Chris
I never could find a solid fix, several workarounds for PC, none for Macs.
The issue does not occur for everyone and we could never replicate it in
our lab."
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