This one bugged me all afternoon - I'd click on, for example, search results, and it just did nothing. Or I'd change the amount per page to over 100 ...and nothing.
Finally, I looked at that bit of phpadmin no-one looks at, the very bottom of the front page!
And it said
Server running with Suhosin. Please refer to documentation for possible issues.
You can read all that if you want, but to cut to the good stuff...
service nginx restart
service php5-fpm restart
and there you go! phpmyadmin all working properly again! Hope this manages to save you the couple of hours I spent looking, and teaches ME to look more closely at the foot of pages...
EDIT: Sorry, mods - I thought I was posting in the hints and tips section. Would you mind moving this post if you feel it belongs there?