i get this problem once in a while, the version is 4.0.1c and it is on my webhost.

Query Failed:SELECT count( DISTINCT users.id ) user_count FROM tracker, users WHERE users.id = tracker.user_id AND PERIOD_DIFF( EXTRACT(YEAR_MONTH FROM NOW( )) , EXTRACT(YEAR_MONTH FROM tracker.date_modified) ) <=1::MySQL error 5: Out of memory (Needed 8388580 bytes)