Created attachment 19365 [details]
Log of the session demonstrating the bug.  I pressed control C to kill the server near the end.

The intel driver does not allow switching between virtual consoles in
NetBSD.  Attempting to switch virtual consoles results in a blank screen
and many error messages like

    (EE) intel(0): underrun on pipe B!

More details:

I have NetBSD-4.99.72/i386 (current as of 2008-09-26).
I have modular xorg built from pkgsrc (also current as of 2008-09-26).
Here are the versions of some of the components:

    modular-xorg-server-1.4.2
    libXxf86dga-1.0.2
    libXxf86misc-1.0.1
    libXxf86vm-1.0.2
    xf86-video-intel-2.4.2
    xf86driproto-2.0.4
    xf86bigfontproto-1.1.2
    xf86vidmodeproto-2.2.2
    xf86miscproto-0.9.2
    xf86dgaproto-2.0.3
    xf86-input-keyboard-1.3.1nb1

If I login on a text console and then run "xinit", the X server starts,
and appears to work correctly.  If I then press alt-control-F1, which is
teh hotkey to switch to a different virtual console in NetBSD's wscons
console driver, that also works correctly.  However, when I press
alt-control-F5 to go back to the virtual console in which the X server is
running, it doesn't work:

Instead of switching back to X, the screen goes blank, flases once or
twice, and then stays blank.

At that point, if I press alt-control-F1, I can return to the text console,
where I see several error messages like

    (EE) intel(0): underrun on pipe B!

I can press control-C to send a SIGINT signal which kills the X server.

Attached to this bug report is a copy of my xorg.conf file (which is the
default that was created by "X -configure"), and the server log file.

The inability to switch between virtual consoles makes it impossible
for me to use the intel driver, which is why I have marked this bug as
"critical".