I've been trying to refurbish my mother's computer for her. It has an Asus A7V880 motherboard(via kt880 chipset) with an Athlon 1.4Ghz CPU, 512 MB of memory, and an old Radeon 7000 AGP card. I've installed Ubuntu 8.04.1 and have it pretty much ready to go. The Xorg log indicates it chooses the "radeon" driver, and AFAICT every other bit of hardware is supported in-kernel.

The problem is this: whenever the computer is rebooted (Quit-->Restart, and also from the menu in GDM), everything seems fine until it gets to the point where GDM should start. Then the monitor just shuts off completely and will not turn back on. VT switching to VT 1-6 has no effect. Once when this happened, I tried going to VT1 and logging in (blindly, with the monitor still shut off), issuing "sudo init 0" and then entering the password but that had no effect. It's possible I made a typo or something, but I'm pretty sure I entered the login/pass, command and sudo password correctly.

The problem does not occur when you actually shut down the computer and then turn it back on - however then, at the same point (between the boot info/usplash ending and GDM starting) the screen will very briefly shut off for 2-3 seconds before coming back to life and giving me a login screen. My sister's similar Ubuntu 8.04.1 box does this same thing, but it restarts just fine without this complete screen shut off problem(her's is an Asus A7N8X-X w/Sempron 1.6Ghz and a radeon 9100 btw).

I have tried removing "splash" from the kernel line in GRUB's menu.list and replacing it with "nosplash", and I've tried setting vga=791 also (1024x768 is the monitor's top resolution, and what the desktop is set at, and what I assume GDM is running at), and I've also tried just "ro quiet" without any "splash" or "nosplash" or "vga=" options at all. I've just now tried uninstalling usplash entirely. None of it has had any effect - if I reboot instead of shutting down completely and turning the computer back on, the screen will turn off when GDM is supposed to show up and nothing I do can get it to turn on again. I can't even use the magic sysreq key to Raise Elephants(...) and reboot safely because I get the same behaviour as when I reboot normally. The only way to get a login screen again is to hold down the power button and power it off without shutting down.

Suspend and Hibernate both work great, if that matters. The monitor comes back to life from power saving mode (when it's meant to be powered off due to no activity) also without issue.

I'm thinking about grabbing a slightly less old radeon card today, if I can find one, but I don't know with anything resembling certainty that the video card is the issue - it was working for her on XP just fine(that was over a year ago though, with a different motherboard - her computer has been in a closet for some time), and it works just fine under Ubuntu apart from this issue.

I'm at my wit's end here, and my mother will not be capable of or intersted in dealing with this if it crops up after she's got her computer back. Any help will be appreciated beyond what words can express.

edit: the guy at the computer shop where I attempted to locate a less old radeon suggested I set a lower resolution. I doubted that would do it, but I added a Display SubSection to the Screen section of the xorg.conf (which was empty beforehand) anyway, like so:
but GDM still appears to be loading at 1024x768 (when starting up from a powered off state), and when rebooting I'm still getting the same screen off behaviour. Setting the resolution lower in GNOME has no apparent affect on GDM, but that's what I expected.

edit2: the problem is not the monitor. swapped out the 14" I was using for my own 19" - same behaviour on reboots.

I have a similar issue with my Xerox monitor and I'm using an Nvidia card, my distro is Mandriva. Mine happens at bootup, for some unknown reason the display doesn't initialise. I have to wait for all hard drive activity to stop then I hit Alt & Ctrl & Del. This reboots the machine and the display then works.

It doesn't happen all the time and it only happens on this machine (I have 5 networked).

Although I have no solution for you, I suggest you use the Alt & Ctrl & Del method to restart your machine (with a graceful shutdown) rather than just powering off.

Thanks for the reply Nexus, I should have tried ctrl+alt+del myself before now actually. It sets off a reboot which doesn't result in the same issue, which is good, that's something at least. It's a bit disappointing though that I'm going to(probably) have to give my mom this same advice after selling her on not using Windows and the virtues of free software.

edit: well, must have been the Radeon 7000 I suppose. Bought an X1650 card and it seems to have done the trick, rebooting is now possible without a blank screen upon login.

u could of also tried ctrl+alt+backspace then gone into a tty but u may of had to do that sequence of key strokes like every 10secs until it stopped.

Glad you've got it sorted.