Impossibly slow DELETEs

Dear You all,

(please tell me if this has already been discussed, I was unable to find any
convincing information)

I'm developing a small application, tied to a PG 7.4 beta 5 (i didn't
upgrade). The DB i use is roughly 20 tales each of them containing at most 30
records (I'm still in development). I can provide a whole dump if necessary.
I access the DB throug IODBC (Suse Linux 8.1), through PHP. The machine
everything runs on is 512M of Ram, 2.5GHz speed. So I assume it should be
blazingly fast.

So here's my trouble : some DELETE statement take up to 1 minute to complete
(but not always, sometimes it's fast, sometimes it's that slow). Here's a
typical one : DELETE FROM response_bool WHERE response_id = '125'
The response_bool table has no foreing key and no index on response_id column.
No foreign key reference the response_bool table. There are 6 rows in the
table (given that size, I assumed that an index was not necessary).

So 1 minute to complete look like I did something REALLY bad.

It is my feeling that doing the same query with psql works without problem,
but I can't be sure. The rest of my queries (inserts, updates) just work fine
and pretty fast.

Can someone help me or point me to a place where I can find help ? I didn't do
any in deep debugging though.

thx,

stF