no idea what version to which this applies as i’ve never installed or configured gallery2, but here’s the process by which i just now debugged one particular gallery2 install…

gallery2/config.php

line 30 - @ini_set(’display_errors’, 1);
line 134 - $gallery->setDebug(’buffered’);

1st error:
Unknown column ‘g2_Item.g_renderer’

grep -r ‘renderer’ *

modules/core/classes/GalleryStorage/schema.tpl:

CREATE TABLE DB_TABLE_PREFIXItem(
…
DB_COLUMN_PREFIXownerId int(11) NOT NULL,
DB_COLUMN_PREFIXrenderer varchar(128),

ALTER TABLE g2_Item ADD g_renderer VARCHAR(128) NULL AFTER g_ownerId;

2nd error:
Unknown column ‘g2_Comment.g_author’

grep -r ‘PREFIXauthor’ *

modules/comment/classes/GalleryStorage/schema.tpl:

CREATE TABLE DB_TABLE_PREFIXComment(
…
DB_COLUMN_PREFIXdate int(11) NOT NULL,
DB_COLUMN_PREFIXauthor varchar(128),

ALTER TABLE g2_Comment ADD g_author VARCHAR(128) NULL AFTER g_date;

perhaps this may help someone else out there.