no unicode with ctrl+shift+u

[VCoolio]

Once upon a time ctrl+shift+u would give me an underlined u, after which I could enter a unicode code for some character. This feature has gone. How do I get it back? Is there something I can reinstall, can I set this keybinding somewhere or does this have to do with my keyboard layout?
As far as I know my keyboard layout and language settings are perfectly normal, env | grep LANG gives me LANG=en_US.UTF-8 and GDM_LANG=en_GB.UTF-8. In language support the box 'enable support to enter complex characters' is ticked, if that has something to do with it. If you ask questions, please also indicate where I can find the answers: there are tons of settings in this range and I don't know where to find them all. Thanks.

[ajgreeny]

Have a look in System > Preferences > Keyboard and go to Layouts > Layout Options to see if you have any settings other than the normal. Anything not default will show as a bold heading so expand that and uncheck the setting. It might just help.

For people like me who wanted the unicode fractions but didn't know how to get them, here they are:-
UNICODE FRACTIONS

Hold down Ctrl+Shift and type u + code below

00BC 1⁄4 vulgar fraction one quarter
00BD 1⁄2 vulgar fraction one half
00BE 3⁄4 vulgar fraction three quarters
2153 1⁄3 VULGAR FRACTION ONE THIRD
2154 2⁄3 VULGAR FRACTION TWO THIRDS
2155 1⁄5 VULGAR FRACTION ONE FIFTH
2156 2⁄5 VULGAR FRACTION TWO FIFTHS
2157 3⁄5 VULGAR FRACTION THREE FIFTHS
2158 4⁄5 VULGAR FRACTION FOUR FIFTHS
2159 1⁄6 VULGAR FRACTION ONE SIXTH
215A 5⁄6 VULGAR FRACTION FIVE SIXTHS
215B 1⁄8 VULGAR FRACTION ONE EIGHTH
215C 3⁄8 VULGAR FRACTION THREE EIGHTHS
215D 5⁄8 VULGAR FRACTION FIVE EIGHTHS
215E 7⁄8 VULGAR FRACTION SEVEN EIGHTHS