Keyboard strangeness in Gnome

[Michael]

Hi,

I´m running Feisty, and despite installing 7.04 with an Ubuntu disk have 
otherwise been using KDE pretty much exclusively.

Today I booted into Gnome, and made the necessary adjustment in 
Preferences > Keyboard for my current layout -- Generic 105-key (Intl) 
PC/United Kingdom International (with dead keys).

However, I now find that apparently without any additional adjustments, 
the Tilda and Circumflex keys need to be pressed twice to register their 
character. Likewise  the Single and Double-quote keys, which instead 
register a slanted single-quote mark and an umlaut respectively.

Presumably this is part of a system to facilitate accented characters, 
but how do I turn it off ;) ?

Regards,

Michael