date and time query

hello,
this is my first post in this forum.

I have the following problem and i really need some help because i am about
to go crazy.

I cannot understand why running this code in sql

select * from lessons where
[date_math] = #29/5/2008# AND ([end_time] #13:00:00# AND [end_time] = #14:
30:00#)

results in a row like this:

id:1150
date_math: 29/5/2008
start_time: 11:30
end_time: 13:00 (!!!)
less_name: my_name

The most crazy thing is that the following query returns no results
select * from lessons where
[date_math] = #29/5/2008# AND ([end_time] #13:00:01(!!!!!!!)# AND [end_time]
= #14:30:00#)

and of course the explanation marks in the parenthesis are not really in my
statement