WordPress database error after installing k2 theme

having installed wp 2.11 then installed k2 3-column theme v0.951, but the following error codes appear:

WordPress database error: [You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘GROUP BY year(post_date), month(post_date), dayofmonth(post_date)’ at line 1]
SELECT DISTINCT post_date FROM GROUP BY year(post_date), month(post_date), dayofmonth(post_date)

would anyone pls help me solve this problem?

thanx a million.