I\'m using Code::Blocks on Ubuntu 10.10. I have connected a Mac keyboard and set the keyboard settings to \"Swiss German Mac\". Now whenever I write an equals sign, followed
Since you're sure it's caused by hitting shift+space, you can check what X itself is doing by.  First, run xev from the command line, hit shift+space and check the output.  For example, I see:
$ xev
KeyPress event, serial 29, synthetic NO, window 0x2000001,
    root 0x3a, subw 0x0, time 4114211795, (-576,-249), root:(414,593),
    state 0x0, keycode 50 (keysym 0xffe1, Shift_L), same_screen YES,
    XLookupString gives 0 bytes:
    XmbLookupString gives 0 bytes:
    XFilterEvent returns: False
KeyPress event, serial 29, synthetic NO, window 0x2000001,
    root 0x3a, subw 0x0, time 4114213059, (-576,-249), root:(414,593),
    state 0x1, keycode 65 (keysym 0x20, space), same_screen YES,
    XLookupString gives 1 bytes: (20) " "
    XmbLookupString gives 1 bytes: (20) " "
    XFilterEvent returns: False
...
Then, run xmodmap -pk and look up the keycode (space should be 65 as above, but check your xev output).
If you see something like
     65         0x0020 (space)
Then X isn't doing this.  On the other hand, if I pick a character key which is modified by shift, I see something like this:
     58         0x006d (m)      0x004d (M)
If you have two or more keysyms for your keycode, X is the culprit.  In that case, something like xmodmap -e 'keycode 65 space' should work.