Invalid keyboard key mapping after installing ubuntu 14.04

[zubin2]

Upon installing Ubuntu 14.04, I find that the back/forward special keys on my kinesis keyboard no longer work (they used to work fine with ubuntu 10.04). Further investigation with xev showed that the correct keypress events are not being sent in this version of ubuntu. When the "back" key is pressed, we get the following sequence of events:

KeyPress for Alt_L
KeyRelease for Alt_L
KeyRelease for Left

The expected sequence should have been:

KeyPress for Alt_L
KeyPress for Left
KeyRelease for Alt_L
KeyRelease for Left

which would have correctly simulated pressing Alt-Left on the keyboard.

This is the stock install (I've not modified any key mappings using xmodmap or any other program).

Would appreciate any help tracking down why there is a missing keypress event, and suggestions for how to fix it. Below is the output from xev.
Thanks!

When "Back" key on keyboard is pressed:
=======================================


KeyPress event, serial 37, synthetic NO, window 0x3600001,
root 0x2bc, subw 0x0, time 120081, (56,178), root:(1751,230),
state 0x0, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES,
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False


FocusOut event, serial 37, synthetic NO, window 0x3600001,
mode NotifyGrab, detail NotifyAncestor


FocusIn event, serial 37, synthetic NO, window 0x3600001,
mode NotifyUngrab, detail NotifyAncestor


KeymapNotify event, serial 37, synthetic NO, window 0x0,
keys: 2 0 0 0 0 0 0 0 1 0 0 0 0 0 2 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0


KeyRelease event, serial 37, synthetic NO, window 0x3600001,
root 0x2bc, subw 0x0, time 120169, (56,178), root:(1751,230),
state 0x8, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES,
XLookupString gives 0 bytes:
XFilterEvent returns: False


KeyRelease event, serial 37, synthetic NO, window 0x3600001,
root 0x2bc, subw 0x0, time 120169, (56,178), root:(1751,230),
state 0x0, keycode 113 (keysym 0xff51, Left), same_screen YES,
XLookupString gives 0 bytes:
XFilterEvent returns: False


When "Alt+Left" is pressed:
===========================


KeyPress event, serial 37, synthetic NO, window 0x3600001,
root 0x2bc, subw 0x0, time 314505, (106,177), root:(1801,229),
state 0x0, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES,
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False


FocusOut event, serial 37, synthetic NO, window 0x3600001,
mode NotifyGrab, detail NotifyAncestor


FocusOut event, serial 37, synthetic NO, window 0x3600001,
mode NotifyUngrab, detail NotifyPointer


FocusIn event, serial 37, synthetic NO, window 0x3600001,
mode NotifyUngrab, detail NotifyAncestor


KeymapNotify event, serial 37, synthetic NO, window 0x0,
keys: 2 0 0 0 0 0 0 0 1 0 0 0 0 0 2 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0


KeyPress event, serial 37, synthetic NO, window 0x3600001,
root 0x2bc, subw 0x0, time 314601, (106,177), root:(1801,229),
state 0x8, keycode 113 (keysym 0xff51, Left), same_screen YES,
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False


KeyRelease event, serial 37, synthetic NO, window 0x3600001,
root 0x2bc, subw 0x0, time 314633, (106,177), root:(1801,229),
state 0x8, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES,
XLookupString gives 0 bytes:
XFilterEvent returns: False


KeyRelease event, serial 37, synthetic NO, window 0x3600001,
root 0x2bc, subw 0x0, time 314673, (106,177), root:(1801,229),
state 0x0, keycode 113 (keysym 0xff51, Left), same_screen YES,
XLookupString gives 0 bytes:
XFilterEvent returns: False