I had the same problem with two machines (32 and 64 bits, see lspci output below)

After turn off "splash" of my kernel, I can get the console and run 'startx' manualy and works.

So, I can see two problems:

1-) splash is broken and the monitor was 100% black after startup
2-) gdm don't works, but startx works.

root@tuxkiller:~# cat /etc/issue
Ubuntu edgy (development branch) \n \l

root@tuxkiller:~# uname -a
Linux tuxkiller 2.6.17-10-386 #2 Tue Sep 26 16:51:46 UTC 2006 i686 GNU/Linux

Thanks a lot!

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32 bit:
00:00.0 Host bridge: Intel Corporation 82865G/PE/P DRAM Controller/Host-Hub Interface (rev 02)
00:02.0 VGA compatible controller: Intel Corporation 82865G Integrated Graphics Controller (rev 02)
00:1d.0 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #1 (rev 02)
00:1d.1 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #2 (rev 02)
00:1d.2 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #3 (rev 02)
00:1d.7 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB2 EHCI Controller (rev 02)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev c2)
00:1f.0 ISA bridge: Intel Corporation 82801EB/ER (ICH5/ICH5R) LPC Interface Bridge (rev 02)
00:1f.1 IDE interface: Intel Corporation 82801EB/ER (ICH5/ICH5R) IDE Controller (rev 02)
00:1f.5 Multimedia audio controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) AC'97 Audio Controller (rev 02)
05:02.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5782 Gigabit Ethernet (rev 03)


64 bit:
00:00.0 Host bridge: Intel Corporation 945G/GZ/P/PL Express Memory Controller Hub (rev 02)
00:01.0 PCI bridge: Intel Corporation 945G/GZ/P/PL Express PCI Express Root Port (rev 02)
00:02.0 VGA compatible controller: Intel Corporation 945G/GZ Express Integrated Graphics Controller (rev 02)
00:02.1 Display controller: Intel Corporation 945G/GZ Express Integrated Graphics Controller (rev 02)
00:1c.0 PCI bridge: Intel Corporation 82801G (ICH7 Family) PCI Express Port 1 (rev 01)
00:1c.1 PCI bridge: Intel Corporation 82801G (ICH7 Family) PCI Express Port 2 (rev 01)
00:1d.0 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI #1 (rev 01)
00:1d.1 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI #2 (rev 01)
00:1d.2 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI #3 (rev 01)
00:1d.3 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI #4 (rev 01)
00:1d.7 USB Controller: Intel Corporation 82801G (ICH7 Family) USB2 EHCI Controller (rev 01)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev e1)
00:1e.2 Multimedia audio controller: Intel Corporation 82801G (ICH7 Family) AC'97 Audio Controller (rev 01)
00:1f.0 ISA bridge: Intel Corporation 82801GB/GR (ICH7 Family) LPC Interface Bridge (rev 01)
00:1f.1 IDE interface: Intel Corporation 82801G (ICH7 Family) IDE Controller (rev 01)
00:1f.2 IDE interface: Intel Corporation 82801GB/GR/GH (ICH7 Family) Serial ATA Storage Controller IDE (rev 01)
00:1f.3 SMBus: Intel Corporation 82801G (ICH7 Family) SMBus Controller (rev 01)
02:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5751 Gigabit Ethernet PCI Express (rev 01)