Indexes not used

Just upgraded from 6.5.3, on solaris

and i'm noticing that indexes are not being used by default

IE: if i have a table

Table "radusage"
Attribute | Type | Modifier
-----------+-------------+----------
datetime | timestamp | not null
account | varchar(64) |
usage | integer |
sent | integer |
recv | integer |
ip | bigint |
host | bigint |
port | smallint |
Indices: idxradaccount,
idxraddate,
idxradoid

and index idxradaccount is

# \d idxradaccount
Index "idxradaccount"
Attribute | Type
-----------+-------------
account | varchar(64)
btree

how come it doesn't use it if i

# explain select * from radusage where account = 'someuser';
NOTICE: QUERY PLAN:

Seq Scan on radusage (cost=0.00..13839.67 rows=5757 width=50)

EXPLAIN

????????????????

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