I'm using Dell Latitude D620. Whenever, I'm pressing the space key, the down arrow key also triggered perform it's action. Here is the log:

KeyPress event, serial 30, synthetic NO, window 0x3200001,
             root 0x10c, subw 0x0, time 2248017, (70,-9), root:(76,39),
    state 0x0, keycode 116 (keysym 0xff54, Down), same_screen YES,
    XLookupString gives 0 bytes: 
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: False

KeyPress event, serial 31, synthetic NO, window 0x3200001,
    root 0x10c, subw 0x0, time 2248018, (70,-9), root:(76,39),
    state 0x0, keycode 65 (keysym 0x20, space), same_screen YES,
    XLookupString gives 1 bytes: (20) " "
    XmbLookupString gives 1 bytes: (20) " "
    XFilterEvent returns: False

KeyRelease event, serial 33, synthetic NO, window 0x3200001,
    root 0x10c, subw 0x0, time 2248083, (70,-9), root:(76,39),
    state 0x0, keycode 65 (keysym 0x20, space), same_screen YES,
    XLookupString gives 1 bytes: (20) " "
    XFilterEvent returns: False

KeyRelease event, serial 33, synthetic NO, window 0x3200001,
    root 0x10c, subw 0x0, time 2248085, (70,-9), root:(76,39),
    state 0x0, keycode 116 (keysym 0xff54, Down), same_screen YES,
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

ClientMessage event, serial 33, synthetic YES, window 0x3200001,
    message_type 0x157 (WM_PROTOCOLS), format 32, message 0x155 (WM_DELETE_WINDOW)

The above log is for a single press+release of spacebar key. I would like to know how to fix that. Thanks.

PS: I'm using the same laptop to post question. If somebody helps to align it into code format, it would be helpful as I can't do that with this keyboard properly.