I was playing with blocks when I pressed the "change" link in the "multiple" column of the admin->modules->manage blocks page.
And I've got this:
Incorrect integer value: '' for column 'multiple' at row 1
UPDATE mdl_block SET name = 'tag_flickr', version = '2007080800', cron = '0', lastcron = '0', visible = '1', multiple = '' WHERE id = '33'
- line 1686 of lib/dmllib.php: call to debugging()
- line 55 of admin/blocks.php: call to update_record()
same for all multiple blocks.
P.D.: I haven't tested this for < Moodle 1.8 but perhaps it should be checked too!