pgadmin or pgsql bug? inserting row

I'm fairly confused by this...I have a table called 'contact' with a
serial id column, so it automatically has this constraint:

ALTER TABLE contact
ADD CONSTRAINT contact_pkey PRIMARY KEY(id);

Now, I tried several times in 1.8.0 to add the row just by typing new
data in the Edit Table window, and I got the same error every time. The
log looked like this (except with the actual name...which was unique
BTW, not that it should matter in this context):

2007-08-07 15:45:53 127.0.0.1 dev LOG: statement: INSERT INTO
contact(name, parent, nickname) VALUES ('[name removed]'::text,
'1'::integer, '[nickname removed]'::text)
2007-08-07 15:45:53 127.0.0.1 dev ERROR: duplicate key violates unique
constraint "contact_pkey"
2007-08-07 15:45:53 127.0.0.1 dev STATEMENT: INSERT INTO contact(name,
parent, nickname) VALUES ('[name removed]'::text, '1'::integer,
'[nickname removed]'::text)

Now, I'm not sure how that's possible, given that I didn't type an ID,
one wasn't being passed to the database, and in any case it's serial so
this shouldn't happen, right?

To make things more interesting, I went over to my own software's UI
that does the same thing, and it worked! In the log, there was:

2007-08-07 15:47:04 127.0.0.1 dev LOG: execute dbdpg_33: insert into
contact (parent,nickname,name) values ($1,$2,$3) returning id
2007-08-07 15:47:04 127.0.0.1 dev DETAIL: parameters: $1 = '1', $2 =
'[nickname removed]', $3 = '[name removed]'

One other detail, after it worked I noticed that the ID returned was one
where there had been a gap in the sequence (i.e., we had entries 1-12
and 14-24, and the new row had id 13.) This may be because the existing
entries had been added with explicit id numbers but the sequence was
probably still at a lower number.

This is pretty befuddling to me. I'm not sure if it's a pgsql issue or
a pgadmin one, but anyway, there's my report.

Kev