Slow Performance with 7.4.1

Hi,
I just installed pg 7.4.1 on a new system P4, 3.2Gh HT, 1GB Mem, RH9 and 
discovered that some of the processes have become extremely slow. Mainly 
I am talking about a SELECT COUNT(*) or VACUUM.

Before running the same database on a P4. 2Ghz 412MB mem, I got the job 
done in some cases half the time.

The weird thing however is, that normal inserts seem to be much faster 
on the new system and I am wondering if it is Postgres or HW related.

Does anyone has an advise ?

Thanks
Alex