Slow query using LIMIT

Doing the following query:
explain analyze SELECT * FROM my.tablename WHERE node = '1234567890' AND
date BETWEEN '2005-03-27' AND NOW() ORDER BY id DESC

takes 1,3 sec. with this result:
 Sort  (cost=52971.52..53033.26 rows=24693 width=93) (actual
time=1141.002..1252.995 rows=25109 loops=1)
   Sort Key: id
   ->  Index Scan using test on tablename  (cost=0.00..50343.48
rows=24693 width=93) (actual time=1.968..363.499 rows=25109 loops=1)
         Index Cond: (((node)::text = '1234567890'::text) AND (date >=
'2005-03-27'::date) AND (date <= now()))
 Total runtime: 1322.876 ms

but when adding a LIMIT it takes almost 2 min...
explain analyze SELECT * FROM my.tablename WHERE node = '1234567890' AND
date BETWEEN '2005-03-27' AND NOW() ORDER BY id DESC LIMIT 10
this result:
 Limit  (cost=0.00..75.24 rows=10 width=93) (actual
time=115401.715..115401.879 rows=10 loops=1)
   ->  Index Scan Backward using unistat_pkey on tablename
(cost=0.00..185781.72 rows=24693 width=93) (actual
time=115401.697..115401.814 rows=10 loops=1)
         Filter: (((node)::text = '1234567890'::text) AND (date >=
'2005-03-27'::date) AND (date <= now()))
 Total runtime: 115402.183 ms

The index test looks like this: "test" btree (node, date, id) and it's a
version 8.0.1
Can anyone please explain to me why it behaves like that and what I can do ?


Thanks,
 Poul