How do I query between two dates using MySQL?

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')

Your query should have date as

select * from table between `lowerdate` and `upperdate`

try

SELECT * FROM `objects` 
WHERE  (date_field BETWEEN '2010-01-30 14:15:55' AND '2010-09-29 10:15:55')