Version:           4.7 (using KDE 4.7.3) 
OS:                Linux

Dead keys (circumflex and umlaut) of some French keyboard does not work. I use a generic keyboard 99 keys, missing in the setup menu keyboards, and auto detected as a 104-key.
The behavior is different depending on the application: it works correctly in Firefox and Google Chrome, for example. In most KDE application, "ô" becomes "^ o". In some other applications it becomes "o" (libreOffice...). Yet xev returns a correct information:
-----
KeyPress event, serial 35, synthetic NO, window 0x8a00001,
    root 0x63, subw 0x0, time 7721664, (-1147,541), root:(208,564),
    state 0x10, keycode 34 (keysym 0xfe52, dead_circumflex), same_screen YES,
    XLookupString gives 1 bytes: (5e) "^"
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: True

KeyRelease event, serial 35, synthetic NO, window 0x8a00001,
    root 0x63, subw 0x0, time 7721773, (-1147,541), root:(208,564),
    state 0x10, keycode 34 (keysym 0xfe52, dead_circumflex), same_screen YES,
    XLookupString gives 1 bytes: (5e) "^"
    XFilterEvent returns: False

KeyPress event, serial 35, synthetic NO, window 0x8a00001,
    root 0x63, subw 0x0, time 7724120, (-1147,541), root:(208,564),
    state 0x10, keycode 32 (keysym 0x6f, o), same_screen YES,
    XLookupString gives 1 bytes: (6f) "o"
    XmbLookupString gives 1 bytes: (6f) "o"
    XFilterEvent returns: True

KeyPress event, serial 35, synthetic NO, window 0x8a00001,
    root 0x63, subw 0x0, time 7724120, (-1147,541), root:(208,564),
    state 0x10, keycode 0 (keysym 0xf4, ocircumflex), same_screen YES,
    XLookupString gives 0 bytes: 
    XmbLookupString gives 2 bytes: (c3 b4) "ô"
    XFilterEvent returns: False

KeyRelease event, serial 35, synthetic NO, window 0x8a00001,
    root 0x63, subw 0x0, time 7724219, (-1147,541), root:(208,564),
    state 0x10, keycode 32 (keysym 0x6f, o), same_screen YES,
    XLookupString gives 1 bytes: (6f) "o"
    XFilterEvent returns: False

FocusOut event, serial 35, synthetic NO, window 0x8a00001,
    mode NotifyNormal, detail NotifyNonlinear
-----

Reproducible: Always

Steps to Reproduce:
Type "ô" using dead key (ie: "^" "o") in various applications: Konsole, Kwrite, Rekonq, aso..

Actual Results:  
^o, ¨i

Expected Results:  
ô, ï

This bug seems persistent in years when seeking a solution on the web. But I've never had with Mandriva, this symptom appears with Kubuntu.