sql query not using indexes

Hello,

I am using last version of postgresql, 7.0.2 on a FreeBSD or Linux box

I create a table:
create table teste (
login text,
datein datetime);

create index teste1 on teste (login);

if I start a query:

explain select * from teste where login = 'xxx'
results:
Index Scan using teste1 on teste (cost=0.00..97.88 rows=25 )

however a query:
explain select * from teste where login > 'AAA'
results:
Seq Scan on teste ....

On a machine running version 6.5 both queries results index scan.

this results that the version 6.5 is faster than version 7.0.2 on this
kind of
query.

Any explanation???

Please???