Created attachment 21072 [details]
xorg.conf

be4bf65d00a28cc77b939f00f115528a9024ab89 "input: don't switch MDs' classes around between SDs" (server-1.6-branch) causes my keyboard layout to not resemble "gb" any more; the transposition of @ and " might suggest it's suddenly become more "us" flavoured. PageUp/Dn is also awry, PageUp previously looking like:

KeyPress event, serial 23, synthetic NO, window 0x600001,
    root 0xb7, subw 0x0, time 7949733, (168,159), root:(170,161),
    state 0x0, keycode 112 (keysym 0xff55, Prior), same_screen YES,
    XLookupString gives 0 bytes:
    XmbLookupString gives 0 bytes:
    XFilterEvent returns: False

and now more like:

KeyPress event, serial 23, synthetic NO, window 0x600001,
    root 0xb7, subw 0x0, time 7850419, (122,86), root:(124,88),
    state 0x0, keycode 112 (keysym 0xffaf, KP_Divide), same_screen YES,
    XLookupString gives 1 bytes: (2f) "/"
    XmbLookupString gives 1 bytes: (2f) "/"
    XFilterEvent returns: False

Updating to xorg-server-1.5.99.3 and applying the four patches from http://www.x.org/wiki/Server16Branch doesn't improve things.  0f36384d0636d6a8d3a8f182be69c72cccd1ff5c of xf86-input-evdev.

xorg.conf attached and unchanged from server 1.5ish setup, with additions of AllowEmptyInput and GrabDevice which seem to be required to make a formerly fine config continue to (somewhat) work (grumble).