I updated to -current (I was previously on the -current dated Tue Mar 22 06:59:13 UTC 2011, IIRC), and now X won't start. The [very short] log ends with:

(EE) ioctl EVIOCGNAME failed: Inappropriate ioctl for device
(EE) PreInit returned NULL for "No brand KVM"

I've been using my KVM for some years without issue until now. When I unplug the KVM and plug my monitor, USB keyboard and mouse directly into the computer, X works.

I tried reverting back to the previous kernel packages (2.6.37.4), but the proprietary Nvidia module wouldn't compile because of the new gcc version. I wasn't prepared to downgrade gcc and who knows what else, so I tried using the generic nv module and also the vesa module, both with 2.6.37.4 and 2.6.37.5. All times resulted in the X error above. The Nouveau driver made the screen go black as soon as it was loaded, and I had to hard reset.

I am currently back to -current but without the use of my KVM, which is an Avocent SwitchviewDVI.

Hrm, are you on 32 or 64bit?

Do you have an xorg.conf file, or do you let the server autoconfigure? If you have an xorg.conf file, then move it out of the way and try letting the server configure itself.

I don't think this is the problem, but try downgrading the libXi package, just for grins and giggles:
http://connie.slackware.com/~rworkman/libXi/

I'm on 32-bit. I tried letting X configure itself, I tried using X -configure (it couldn't find a screen), and I tried my usual method, which is letting X configure itself mostly but with the Device and Screen settings only, in xorg.conf (which is my usual setting, required to use the proprietary Nvidia driver). Always it produced the error above, except when using the /root/xorg.conf.new from X -configure.

I'll try downgrading libXi when I get home tonight.

Thank you.

Downgrading to your linked libXi 1.4.1 made no difference, even after updating to today's -current changes.

The -current update dated Tue Mar 29 22:58:09 UTC 2011 has fixed this.

However, Lomoco no longer works with my Logitech MX510 mouse. It used to detect it as some generic mouse (IIRC - it definitely didn't detect it as an MX510), because of the KVM. However, telling it to set the mouse to 800DPI or 400DPI did work. Now, it doesn't do anything but output "008.002: 046d:08ad Unsupported Logitech device: ?". I'm not expecting anybody to be able to help with that (it would be great if they could, though!), just saying that the latest update fixed my original problem.