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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