Is my Mac Pro eating monitors? Am I going crazy? A great mystery....

Question

Something very bizarre is happening, and it doesn't make a lot of sense to me. Maybe someone here can offer a theory. Here's my setup, and here's what's been happening....
Mac Pro (early 2009), 2.66 GHz Quad-Core, 8 gigs of RAM, running Mac OS X 10.5.7.
ATI Radeon HD 4870. A very nice system, still has that new Mac smell.
Primary display is a 24" HannsG HH251 (a nice, if inexpensive large flat-panel).
Secondary display is a 20" Viewsonic VP200s. This is an older flat-panel (about 4 years old). I own three of these Viewsonic displays - they were a good primary workhorse monitor in their day, now I use them (mostly) as the 2nd monitor on my Macs and PCs (I have several).
Here's what's been happening...
The primary display is fine. The secondary display has been "failing". When I first hooked up the Viewsonic monitor (as the second display), it was fine. We'll call this "Viewsonic #1". After a couple of months, though, it started flickering - not a subtle flicker (as you might see with a low refresh rate), but a complete, violent flicker where the screen redraws instantly. At first, the big flicker would only occur intermittently - once every few minutes - but eventually it would start happening more and more frequently, then happened every second or two, then became constant - to the point where stuff on that monitor became completely unusable - I couldn't see the cursor clearly, couldn't close windows, etc. Initially, if I turned the monitor off for a moment, then back on, it would come back briefly. But the big flicker would start again soon. Powering down the computer and leaving it off for a while (like overnight), then starting it up again, the 2nd display (Viewsonic #1) would be OK for a while, but eventually the flashing started again. Rinse, lather, repeat.
I figured some hardware component was going bad - probably the monitor, but I was hoping it might be the cable or perhaps even the video card (still under warrantee). So I did a little swapping to see: I used a different video cable. Same problem. I thought, "****, the display is toast." I was bummed, but not heartbroken: I had 2 more of these monitors, and I could swap another one in. So I pulled an identical monitor from an older Windows PC that I'm not using much (we'll call this Viewsonic #2), and swapped that. As I suspected, using Viewsonic #2, the 2nd display on the Mac Pro came up nice and flicker-free, rock-steady and looking good. And when I boot up the Windows PC that now has the "bad" display (Viewsonic #1, removed from the Mac Pro), sure enough, it's flickering and flashing and just about impossible to use.
OK, so this seemed to confirm my theory: that Viewsonic #1 was simply in the process of dying. No hardware lasts forever, and although I'm used to getting 5-10 years out of my monitors (really - I've been at this a long time), that rule of thumb is from CRT days - I figured maybe flat panel LCDs only go about 5 years. I shrugged and made my peace with it. Since I was back in 2-monitor heaven, I wasn't worried about it (since I don't need to use the Windows PC with the funky display).
Turns out, there's more to it. This is where it gets strange.
It was about 3 or 4 days ago that I did the monitor swap. Since then, Viewsonic #2 has been fine, as I expected, solid, looking good. But about 6 hours ago, I was shocked to see Viewsonic #2 - now hooked up as my secondary display on the Mac Pro - has just started the same flicker. And it started getting worse, pretty quickly. Within an hour or so, it was becoming unusable. Once again, turning it off helped - a little - and so did shutting done the Mac and leaving it off. But soon after powering it up, it starts going haywire again. It's got the exact same problem that killed the other monitor.
I am thinking that the odds of two different monitors failing (hardware going bad) like this is extremely unlikely. I know it's not the cable or plug, because when I moved Viewsonic #1 to a different computer, it's still broken. I don't think it's the video card, because the "badness" moves with the bad monitor, and the primary display is fine.
The only think that makes any sense (and I'll admit it doesn't make much), is that there's something about this Mac Pro that is causing the 2nd monitor to fail - actually damaging the monitor. That sounds pretty unlikely, but it's the least unlikely think I can think of. Could it be outputting a signal that kills the monitor hardware? I know that sounds crazy....I'm open to suggestions if anyone has another theory.
I've never heard of a computer (or a video card) causing a display to fail, but given the fact that these monitors were both fine before I hooked them up to this Mac, and that both of them seem to have gone belly-up now (and they stay broken if moved back to another computer) really leaves me scratching my head.
What on earth is happening here? Any ideas?

Answer 1

Hi Ltm,
Is your set up is like this? Main monitor attached to dvi port on 4870, other displays attached to the mini port via adapter?
If it is, those mini ports have been the source of many peoples problems here. Maybe not even so much the ports but the adapters. Some seem to work better than others. I bought two in the 20 dollar range from Apple and they both worked poorly (and I have all Apple displays!). Apparently Apple sells one for about 100 bucks that works the best, but I changed cards before buying that.
OWC has an interesting mini-display port connecter now that looks good but also goes for a hundred or so.
But what is precisely going on with your Viewsonics to seemingly destroy them, I don't know. I've read of similar problems to yours, but the displays never stayed in a poor condition after the problem was found. Yours is the first post I've read of displays being actually killed off.
If you could take the now damaged display and one that isn't to an Apple store to try on one of their Macs, maybe they could turn up something for you, an incompatibility somewhere maybe. But it's a pretty bizarre situation made worse by Apples decision to introduce unnecessary variables by going with that mini-display port.