Možná to souvisí s case sensitive prefixem, který jsi použil pro tabulky v databázi?
Ok, dig deeper into the MySQL settings and found out that this could be a real issue if you define a prefix with Case sensitive letters, the check will fail :
http://dev.mysql.com/doc/refman/5.1/en/identifier- case-sensitivity.html
Here is the patch for this case :
http://code.google.com/p/nextgen-gallery/source/de tail?r=823