Comment 5 for bug 229966

In Ubuntu 10.04 with the default Spanish keyboard layout, AltGr + 4 produces ~.
This has been the case since April 2008,
0fb00efe (svu 2008-04-23 18:12:14 +0000 17) key <AE04> { [ 4, dollar, asciitilde, dollar ] };

Could you please try again with Ubuntu 10.04?

The situation you get when you have to press the key and then a space, is that somehow the dead_tilde is being mixed up.
For the Spanish layout, you get dead_tilde if you press AltGr + (that key that shows the Exclamation Down character).

So, if you still get the problem, then you either
1. have a mixed up keyboard model that mixes the '4' key with 'exclamation down'.
2. or you may have enabled by accident IBus (see Language Support, make sure that IBus is disabled).