When mysqli driver is used, and some databases exist this exception is displayed randomly making PMA useless. AFAIR it's bogus exception, a bug in PHP 5.x. There is a very quick fix for this bug - all you have to do is add one line to /libraries/dbi/mysqli.dbi.lib.php, it works fine when added as close to beginnig as possible. The line is:
This bug is present in all PMA versions above 3.0. I would appreciate if it would be fixed in further versions. Now I have to fix it myself every time I install new PMA.