unable to update a field in AppExchange

Hi,

I was unable to update a field with AppExchange even though I can do the update using web interface.

I am new to salesforece. Is there something that I am not aware of (like some special permission to update a field by AppExhange)?

Here's my code. The strange thing is 'Application__c', 'Download_ID__c', 'Additional_Email_Addresses' and 'Bank_Name__c' got updated, but not 'Order_Complete__c', 'ListPrice', 'UnitPrice'. That's why I think there is a permission problem. However, If I can update 'Order_Complete__c' by using web interface, why can I not with AppExchange?

      sforce.OpportunityLineItem oli = new sforce.OpportunityLineItem();
      oli.Id = "XXX"; //I put in the real id here
      oli.Order_Complete__c = true;
      oli.Application__c="test1-1";
      oli.Download_ID__c="test2-2";
      oli.ListPrice = 1.0;
      oli.UnitPrice = 3.0;
      oli.Additional_Email_Addresses__c = "test3-1";
      oli.Bank_Name__c="test 4-1";

Thanks in advance.

-ann