Max time queries

Heres an oddity. Why would it take more time to not find an answer than it would to find one?
Here are my 2 queries.
The Cold Fusion output of the query is followed by an explain analyze.

maxTime (Records=0, Time=2223ms)
SQL =
select cr.start_time as max
from call_results cr, timezone tz, lists l
where (cr.start_time between '10/15/2002 08:00' and '10/15/2002 23:00')
and l.full_phone = cr.phonenum
and l.area_code = tz.area_code
and tz.greenwich = '-7'
and cr.project_id = 11
and l.client_id = 8
order by cr.start_time desc
limit 1

NOTICE: QUERY PLAN:

Limit (cost=0.00..1544.78 rows=1 width=49) (actual time=2299.11..2299.11 rows=0 loops=1)
-> Nested Loop (cost=0.00..1266550.38 rows=820 width=49) (actual time=2299.10..2299.10 rows=0 loops=1)
-> Nested Loop (cost=0.00..776978.04 rows=90825 width=42) (actual time=0.84..1849.97 rows=9939 loops=1)
-> Index Scan Backward using start_time_idx on call_results cr (cost=0.00..6569.39 rows=6693 width=22) (actual time=0.38..303.58 rows=9043 loops=1)
-> Index Scan using full_phone_idx on lists l (cost=0.00..114.94 rows=14 width=20) (actual time=0.15..0.16 rows=1 loops=9043)
-> Index Scan using area_code_idx on timezone tz (cost=0.00..5.38 rows=1 width=7) (actual time=0.04..0.04 rows=0 loops=9939)
Total runtime: 2300.55 msec

maxTime (Records=1, Time=10ms)
SQL =
select cr.start_time as max
from call_results cr, timezone tz, lists l
where (cr.start_time between '10/15/2002 08:00' and '10/15/2002 23:00')
and l.full_phone = cr.phonenum
and l.area_code = tz.area_code
and tz.greenwich = '-8'
and cr.project_id = 11
and l.client_id = 8
order by cr.start_time desc
limit 1
NOTICE: QUERY PLAN:

Limit (cost=0.00..331.03 rows=1 width=49) (actual time=1.19..1.53 rows=1 loops=1)
-> Nested Loop (cost=0.00..1266550.38 rows=3826 width=49) (actual time=1.19..1.52 rows=2 loops=1)
-> Nested Loop (cost=0.00..776978.04 rows=90825 width=42) (actual time=0.84..1.10 rows=2 loops=1)
-> Index Scan Backward using start_time_idx on call_results cr (cost=0.00..6569.39 rows=6693 width=22) (actual time=0.39..0.48 rows=2 loops=1)
-> Index Scan using full_phone_idx on lists l (cost=0.00..114.94 rows=14 width=20) (actual time=0.30..0.30 rows=1 loops=2)
-> Index Scan using area_code_idx on timezone tz (cost=0.00..5.38 rows=1 width=7) (actual time=0.19..0.20 rows=1 loops=2)
Total runtime: 1.74 msec