The following query:
SELECT * FROM `objects` WHERE (date_field BETWEEN \'2010-09-29 10:15:55\' AND \'2010-01-30 14:15:55\')
returns nothin
Your second date is before your first date (ie. you are querying between September 29 2010 and January 30 2010). Try reversing the order of the dates:
SELECT * FROM `objects` WHERE (date_field BETWEEN '2010-01-30 14:15:55' AND '2010-09-29 10:15:55')