problems with unique key on table with serial

Dear all,

I have the following problem.

I have a table (among others of course) that has the following structure:
CREATE TABLE "tblserver" (
"ID_Server" oid DEFAULT nextval('tblserver_id_server_seq'),
"Svr_Name" varchar(150) NOT NULL,
"IP_Address" inet NOT NULL DEFAULT '0.0.0.0',
"Location" varchar(255),
"Description" text,
"C_Date" date,
"C_Time" time,
"C_User" varchar(42),
"L_Date" date,
"L_Time" time,
"L_User" varchar(42),
"C_Update" int4,
"TimeStamp" timestamp,
PRIMARY KEY("ID_Server")) \g

and a sequence for that (I create the sequence first and then the table)
CREATE SEQUENCE tblserver_id_server_seq \g

than I have two functions
CREATE FUNCTION fncdatetime_ains() returns opaque as
'begin
new.TimeStamp := now();
new.C_Date := current_date;
new.C_Time := current_time;
new.C_User := getpgusername();
return new;
end;'
language 'plpgsql' \g

CREATE FUNCTION fncdatetime_aupd() returns opaque as
'begin
new.TimeStamp := now();
new.L_Date := current_date;
new.L_Time := current_time;
new.L_User := getpgusername();
return new;
end;'
language 'plpgsql' \g

and two triggers calling the functions:
CREATE TRIGGER trgInsServer before insert on tblserver
for each row execute procedure fncdatetime_ains() \g

CREATE TRIGGER trgUpdServer before update on tblserver
for each row execute procedure fncdatetime_aupd() \g

When I create the structure I do an insert into the table so that
I have a default-dataset. This is because I have some dependencies
on this table and I need kind of a blind dataset in it.

INSERT INTO tblserver ("ID_Server", "Svr_Name", "IP_Address",
"Location", "Description")
VALUES (1, 'slughammer', '24.3.19.73', 'slugmania',
'db-design by chris') \g

Now, when I try to insert a second dataset in the table from my
Web application I get the error-message:

Warning: PostgreSQL query failed: ERROR:
Cannot insert a duplicate key into unique index tblserver_pkey in
/sitebuilder/_inc/fnc_server_adm.php on line 178

What is that supposed to mean??? I thought When I have a sequence
pSQL determines the new PKey by itself on an insert?

Pleeease anyone give me a hint - just a small one ;-)

chris