I've been using unstable Debian for about 18 months with relatively few problems.

Today I've apt-get upgraded and played around with xhost host (xhost +local:[account]) attempting to get a Java applet working.

Upon restarting my computer the graphical login fails to appear (the screen goes to black as if it is about to launch and a white horizontal line quickly flashes on the screen, then returns to command line) and the following was displayed:

Starting K Display Manager: kdm.
Running local boot scripts (/etc/rc.local).
Not starting X display manager (xdm); it is not the default display manager.

If I try to run xhost now, by the way, it responds: 'xhost: unable to open display ""'. Any ideas?

Edit: when I attempt to "dpkg-reconfigure xserver-xfree86" (either as root or su) nothing happens, it returns to the command line.
Edit2: My wireless adaptor also seems to have stopped working. This is really not my day.

I really don't know but it may still be some permission problem, some x settings may have been disabled as root for security reasons, for example, google for it...

Have you tried aptitude (apt-get) remove --purge kdm ... aptitude install kdm?

Could also be an xorg issue, but dpkg-reconfigure xorg-xserver doesn't work any more. You'll have to edit /etc/X11/xorg.conf manually. With a little luck, you may have a back-up of your old xorg.conf file created when it was last edited.

I think there may also be a (non-Debian) Xorg utility named Xorg -configure or something like that.

******
If your upgrade included a new kernel, that would certainly have wiped out your wireless. Should be easy to fix, tho.

i'm having a similar issue with xfce on debian etch... about to post a new thread with details of that.

Thanks for the replies so far. As yet, the problem is still unresolved. I have discovered that others have been having the problem, it is to do with a new xserver-xorg-core.

rickh: The computer isn't connecting to a network at the moment (no wireless) so I don't want to purge at the moment (it would have to redownload it, right?). I'm not great at command line, how do I go about replacing the conf file with a backup?

Edit: When I run startx I get the following error:
"Fatal server error:
failed to initialize core devices
(**) RADEON(0): RADEONLeaveVT
(**) RADEON(0): RADEONRestore
(**) RADEON(0): RADEONRestoreMode()
(**) RADEON(0): RADEONRestoreMode(0x8207ca8)
(**) RADEON(0): RADEONRestoreMemMapRegisters() :
(**) RADEON(0): MC_FB_LOCATION : 0x1fff0000
(**) RADEON(0): MC_AGP_LOCATION : 0x27ff2000
(**) RADEON(0): Map Changed ! Applying ...
(**) RADEON(0): Map applied, resetting engine ...
(**) RADEON(0): Updating display base addresses...
(**) RADEON(0): Memory map updated.
(**) RADEON(0): Programming CRTC1, offset: 0x00000000
(**) RADEON(0): Ok, leaving now...
XIO: fatal IO error 104 (connection reset by peer) on X server ":0.0"
after 0 requests (0 known processed) with 0 events remaining.

If you can't fix this any other way, try this:

aptitude install apt-file
apt-file update

Then find the files you have modified recently and find out which packages they belong to:

find / -mtime -2| -exec apt-file --package-only search {} \;

Now you'll have a list of packages that you _might_ want to reinstall. In the above example "find" will find files that are modified 0-2 days ago. See "man find" for more info.

In order to reinstall these without running into dependency problems do a

dpkg --purge --force-all packagename

and then reinstall the package with aptitude. If it still does not work, remove all remotely relevant files and directories from your home dir.

Hope this helps.

I just remember one thing: when xorg is updated you may have to reinstall the video driver, else all is blackout; that's the case with my nvidia anyhow