Choosing to restrict forum ratings by date causes an error as described in this discussion: http://moodle.org/mod/forum/discuss.php?d=175888. The problem is that the code in mod/forum/lib.php that does the date comparison tries to compare against a non-existent column. This defect was introduced with the fix for MDL-26838.
The line that reads
if ($info->timecreated < $info->assesstimestart || $info->timecreated > $info->assesstimefinish) {
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should be changed to
if ($info->created < $info->assesstimestart || $info->created > $info->assesstimefinish) {
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Searching on "timecreated" will take you directly to the line with the defect.