Error with @DBLookUp command: 'Entry not found in index'

I encountered an error when I used the @DBLookup command. My database is like an address book; it is for Web use and I'm going to view my form using Internet Explorer. My form function is to retrieve the mail file data based on the user's name. The first field in my form is used to retrieve the username and the second one, mailbox, is to retrieve the mail file information in the view "byUsername," which consists of two columns, Fullname and Mailfile.

The error I encountered reads, "Entry not found in Index." Only two entries were working properly, mine and my boss' name.

The syntax I used to retrieved the info are:

field CurrentUser:=@Name([CN];@username);

field Mailbox:=@dblookup("notes":
"noCache";@DBname;"byUsername";
CurrentUser;2;
[FailSilent]);

Can you please help me?