I have a similar bug on my ubuntu test box with the following specs.

Specificiations 

Ubuntu Feisty 7.04 
RevisMion history / 
Initial install Dapper Drake, Upgraded From Dapper To Edgy and from Edgy to Feisty. 

CPU AMD athlon 64 3200 +
Video card Ati Radeon X800 pro.
Installed FGLRX driver.
Monitor Samsung 940BF tft screen connected via a DVI cable.

Installed dapper without problems, and was able to perform the upgrades during one year. 
During my Linux use i tried to tame X but I encountered some problems. 

1. When my monitor is auto detected as "Plug and play" in the options, the black screen of death appears and only single user mode enables me to restore xorg.conf
2. Manually defining my monitor as a 1280X1024 monitor with a 74 hz refresh rate solves my problem.
3 Defining my monitor as a generic TFT screen with a resolution of 1280X1024 leads to image corruption and a non-working mouse.

But the tricky part was, that I wanted to reinstall feisty from CD, to start anew to solve some other problems, the black screen appears again when booting from the installer CD. 
And of course X dies a horrible death. But at least I encounter a similar prolem with a functional X system, so here are some xorg.0.log entries from a "black screen situation". 

First Xorg.0.log from my working system (note, it already contains errors).

Xorg.0.log from working system

tijssenn@tijssenn-desktop:/var/log$ cat Xorg.0.log.old | grep EE
        (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(II) Loading extension MIT-SCREEN-SAVER
(EE) fglrx(0): === [swlDalHelperAddCustomizeMode] === CWDDEDI_DisplayGetSetModeTimingOverride failed: 7
(EE) fglrx(0): === [swlDalHelperAddCustomizeMode] === CWDDEDI_DisplayGetSetModeTimingOverride failed: 7
(EE) fglrx(0): === [swlDalHelperAddCustomizeMode] === CWDDEDI_DisplayGetSetModeTimingOverride failed: 7
(EE) fglrx(0): === [swlDalHelperAddCustomizeMode] === CWDDEDI_DisplayGetSetModeTimingOverride failed: 7
(EE) fglrx(0): === [swlDalHelperAddCustomizeMode] === CWDDEDI_DisplayGetSetModeTimingOverride failed: 7
(EE) fglrx(0): === [swlDalHelperAddCustomizeMode] === CWDDEDI_DisplayGetSetModeTimingOverride failed: 7
(EE) fglrx(0): === [swlDalHelperAddCustomizeMode] === CWDDEDI_DisplayGetSetModeTimingOverride failed: 7
(EE) fglrx(0): === [swlDalHelperAddCustomizeMode] === CWDDEDI_DisplayGetSetModeTimingOverride failed: 7
(EE) fglrx(0): === [swlDalHelperAddCustomizeMode] === CWDDEDI_DisplayGetSetModeTimingOverride failed: 7
(EE) fglrx(0): === [swlDalHelperAddCustomizeMode] === CWDDEDI_DisplayGetSetModeTimingOverride failed: 7
(EE) fglrx(0): === [swlDalHelperAddCustomizeMode] === CWDDEDI_DisplayGetSetModeTimingOverride failed: 7
(EE) fglrx(0): === [swlDalHelperAddCustomizeMode] === CWDDEDI_DisplayGetSetModeTimingOverride failed: 7
(EE) fglrx(0): === [swlDalHelperAddCustomizeMode] === CWDDEDI_DisplayGetSetModeTimingOverride failed: 7
(EE) fglrx(0): GART is not initialized, disabling DRI
(EE) AIGLX: Screen 0 is not DRI capable
(EE) xf86OpenSerial: Cannot open device /dev/wacom
(EE) xf86OpenSerial: Cannot open device /dev/wacom
(EE) xf86OpenSerial: Cannot open device /dev/wacom
(EE) AIGLX: Screen 0 is not DRI capable
(EE) xf86OpenSerial: Cannot open device /dev/wacom
(EE) xf86OpenSerial: Cannot open device /dev/wacom
(EE) xf86OpenSerial: Cannot open device /dev/wacom
tijssenn@tijssenn-desktop:/var/log$                                          

Xorg.0.log from " Black screen of death" situation

(II) Loading extension MIT-SCREEN-SAVER
(EE) fglrx(0): GART is not initialized, disabling DRI
(EE) AIGLX: Screen 0 is not DRI capable
(EE) xf86OpenSerial: Cannot open device /dev/wacom
(EE) xf86OpenSerial: Cannot open device /dev/wacom
(EE) xf86OpenSerial: Cannot open device /dev/wacom

	(WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(WW) The directory "/usr/share/X11/fonts/cyrillic" does not exist.
(WW) fglrx: No matching Device section for instance (BusID PCI:1:0:1) found
(WW) fglrx(0): GetVBEMode failed
(WW) fglrx(0): Failed to open DRM connection
(WW) fglrx(0): No DRM connection for driver fglrx.
(WW) fglrx(0): ***********************************************
(WW) fglrx(0): * DRI initialization failed!                  *
(WW) fglrx(0): * (maybe driver kernel module missing or bad) *
(WW) fglrx(0): * 2D acceleraton available (MMIO)             *
(WW) fglrx(0): * no 3D acceleration available                *
(WW) fglrx(0): ********************************************* *

I tried a fresh install and the Feisty installer locks up with the reported black screen of death. I assume this bug may be caused by the default selection of plug and play for a monitor.