oracle forms 10g runtime timeout

i have this code in a when-validate-item trigger

declare
x number;
c varchar2(5);
n varchar2(25);
begin
select COUNT(*) into x from CUSTOMERS where CUSTOMERS.cus_name=:output_header.text_item48;
if x > 0
  then
  NULL;
else
  IF SHOW_ALERT('ALERT56')= ALERT_BUTTON1 THEN
  select to_char(max(customers.cus_id)+1) into c from customers;
  n:=to_char(:output_header.text_item48);
  insert into customers(cus_id,cus_name) values(c,n);
  end if;
END IF;
end;'

this code should check if the customer name entered already exists , if NOT i want to create a new customer the problem is when i press the alert button1,, instead of inserting a new customer(record) into the customers table , the form become not responding for ever can you please help me the problem is in the insert statement; thanks in advance

Seems :output_header.text_item48 is already a char item so no need to convert using to_char, test with the following code:

declare
x number;
c varchar2(5);
n varchar2(25);
begin
select COUNT(*) into x from CUSTOMERS where CUSTOMERS.cus_name=:output_header.text_item48;
if x > 0
  then
  NULL;
else
  IF SHOW_ALERT('ALERT56')= ALERT_BUTTON1 THEN
  select to_char(max(customers.cus_id)+1) into c from customers;
  n:= :output_header.text_item48;
  insert into customers(cus_id,cus_name) values(c,n);
  commit;
  end if;
END IF;
end;