Mac Pro Display flicker & failure to boot

Question

Hello people who are smarter than me.
I have a 2008 Mac Pro 3.2/ 8CX 8800GT with the original Geforce video card installed.  When I turn the machine on I get a grey screen with a black bar at the top, with no evidence of an actual boot (such as a darker grey apple in the middle of the screen.
After a minute or so, the screen retains the form of the black and white horizontal bar at the top but adds a rapidly cycling/strobing organge red and yellow flicker reminiscent of the old Monty Python crazy title screens....  It looks like this if you blink fast enough... or take a still photo.
I live in Haiti, where a fair amount of dust is constantly invading my tower, so I've had dust related issues before with memory... THis time, I don't think it's that.  I've cleaned out the tower with pressurized air, reseated the memory and reseated the video card as well, to no advantage.  The problem first came when the computer was working fine and while my daughter was opening a page on Firefox the screen just started jittering with this little color show.  At the time, though, you could still see the desktop behind all the flickering.  Now the computer doesn't seem to even boot.  If I have to fly to the states to fix this, I'd love to not have to haul the whole machine, so if we can get this down to a couple likely parts that I could travel with, test and replace, that would be great.  This is a hardware issue, right? Would video card failure make sense of this AND the failure to boot?  AND if I do replace it, is the ATI Radeon HD 5770 Graphics Upgrade Kit still the ticket?  If you help me, you'll be helping a lot of Haitians too, as I use this computer for humanitarian work with the Apparent Project.  Help me Obi Geeks, you're my only hope!

Answer 1

Okay, so after doing all of the above, the computer still takes between 40 seconds and 1 minute or so to boot up, and the VersionCue messages still appear. However I discovered that the "kdcmond cannot retrieve..." messages disappeared after I disabled my ethernet connections. So at least I know that that had nothing to do with the extended boot-up time.
I have heard that the more RAM you have, the longer it takes to boot due to the RAM count. Since I have 10 GB, maybe this is why?
I've included the most recent Console messages below:
22/4/08 9:56:16 AM com.apple.launchctl.System[2] launchctl: Please convert the following to launchd: /etc/mach_init.d/dashboardadvisoryd.plist
22/4/08 9:56:16 AM com.apple.launchd[1] (com.adobe.versioncueCS3) Unknown key: ServiceDescription
22/4/08 9:56:16 AM com.apple.launchd[1] (org.cups.cups-lpd) Unknown key: SHAuthorizationRight
22/4/08 9:56:16 AM com.apple.launchd[1] (org.cups.cupsd) Unknown key: SHAuthorizationRight
22/4/08 9:56:16 AM com.apple.launchd[1] (org.ntp.ntpd) Unknown key: SHAuthorizationRight
22/4/08 9:56:39 AM com.apple.SystemStarter[28] Starting Aladdin USB daemon
22/4/08 9:56:39 AM org.ntp.ntpd[25] Error : nodename nor servname provided, or not known
22/4/08 9:56:39 AM com.apple.launchd[1] (com.apple.UserEventAgent-LoginWindow[74]) Exited: Terminated
22/4/08 9:56:39 AM com.apple.launchctl.Aqua[90] launchctl: Please convert the following to launchd: /etc/machinit_peruser.d/com.adobe.versioncueCS3.monitor.plist
22/4/08 9:56:42 AM com.apple.launchd[82] (0x1011e0.VersionCueCS3monitor) Failed to check-in!