Ctrl-Alt-F1 not working from X

Question

I have a system running Debian 5.0 that doesn't respond to Ctrl+Alt+F# (1-6)

Check if Ctrl, Alt, F1 and F2 are intercepted correctly...

$ DISPLAY=:0 xwininfo

xwininfo: Please select the window about which you
          would like information by clicking the
          mouse in that window.

xwininfo: Window id: 0xe00002 (has no name)
...

$ xev -display :0 -id 0xe00002
KeyPress event, serial 16, synthetic NO, window 0xe00002,
    state 0x10, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES,

KeyPress event, serial 16, synthetic NO, window 0xe00002,
    state 0x10, keycode 37 (keysym 0xffe3, Control_L), same_screen YES,

KeyPress event, serial 16, synthetic NO, window 0xe00002,
    state 0x10, keycode 67 (keysym 0xffbe, F1), same_screen YES,

KeyPress event, serial 16, synthetic NO, window 0xe00002,
    state 0x10, keycode 68 (keysym 0xffbf, F2), same_screen YES,

..They are.

However, xev does not report Ctrl+Alt+F1 as one single event. Does that mean, X does not correctly interpret that sequence?

Check if X is configured to ignore Ctrl+Alt+F#..

$ grep -i dontvtswitch /etc/X11/xorg.conf

..It isn't

But killing X with Ctrl+Alt+Backspace allows me to switch ttys.

The Xorg.0.log at pastebin.

How enable tty switching when running X?

The root filesystem is mounted as read-only. Can that affect how X setups up keyboard mappings? Tried mounting as read-write but the problem persists. Haven't been able to make the system boot up in read-write (I've set the boot options in the bootloader but something happens during boot that remounts the rootfs as readonly).

Answer 1

Had the same with Microsoft Natural Keyboard 4000. The answer was surprisingly simple. This keyboard had, either by default or my sloppiness, F-Lock enabled. The key presses of F1-F12 were treated as 'Help', 'Undo', 'Redo', 'New' (and so on) actions. Pressing F-Lock (right to F12 key) deactivated function lock, restoring original function keys assignments.