Jdbc/postgres performance

Hi

We are facing performance problems in postgres while executing a query.
When I execute this query on the server it takes 5-10 seconds. Also I
get good performance while executing this query from my code in java
with the hard codes values. I face severe performance problems when I
run it using a prepared statement.

The query is as follows:
Select events.event_id, ctrl.real_name, events.tsds, events.value,
events.lds, events.correction, ctrl.type, ctrl.freq from
iso_midw_data_update_events events, iso_midw_control ctrl where
events.obj_id = ctrl.obj_id and events.event_id > 68971124 order by
events.event_id limit 2000

The above query executes in 5-10 seconds.

However the below query executes in 8 mins:

Select events.event_id, ctrl.real_name, events.tsds, events.value,
events.lds, events.correction, ctrl.type, ctrl.freq from table events,
iso_midw_control ctrl where events.obj_id = ctrl.obj_id and
events.event_id > ?::bigint order by events.event_id limit ?

setLong(1, 68971124);
setInt(2, 2000);

The table has close to 5 million rows. The table has the following
index:

iso_midw_data_update_events_event_id_key
iso_midw_data_update_events_lds_idx
iso_midw_data_update_events_obj_id_idx

The table is described as follows:

Columns_name data_type type_name column_size
lds 2 numeric 13
obj_id 2 numeric 6
tsds 2 numeric 13
value 12 varchar 22
correction 2 numeric 1
delta_lds_tsds 2 numeric 13
event_id -5 bigserial 8

Please tell me what I am missing while setting the prepared statement. I
am using postgres7.4.2. and postgresql-8.1-407.jdbc3.jar.

Thanks

Regards

Rohit