Massive performance differences

Hi all,

I'm running the same database on two systems:

A) Debian PostgreSQL 7.4.7
B) SuSE PostgreSQL 7.3.4

Both machines have approx. 1GHz and 1GB RAM.
The amount of data is almost equal (+- 10%). But I'm facing
huge performance differences. For instance, a simple sequential
scan results in the following query plans:

explain analyze select * from veranstaltung_original order by semester;

A) ------------------------------------------------------------

Sort (cost=734.74..747.77 rows=5210 width=232) (actual time=89.935..92.730
rows=5210 loops=1)
Sort Key: semester
-> Seq Scan on veranstaltung_original (cost=0.00..413.10 rows=5210
width=232) (actual time=0.011..7.852 rows=5210 loops=1)
Total runtime: 96.900 ms

B) ------------------------------------------------------------

Sort (cost=3054.08..3067.74 rows=5467 width=223) (actual
time=2568.10..2573.02 rows=5467 loops=1)
Sort Key: semester
-> Seq Scan on veranstaltung_original (cost=0.00..2714.67 rows=5467
width=223) (actual time=1936.68..2506.83 rows=5467 loops=1)
Total runtime: 2579.08 msec

------------------------------------------------------------

Could this be due to the different PostgreSQL versions?
Is there a typical cause for such performance problems?
How can I find out what's wrong with installation (B)?

Thanks in advance!

-- Andreas