CASTING Error... 2000 and 2005 Different

I get an error with SS2000 that I don't get with SS2005.  I used the same scripts below to create all 3 items on both systems.
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NO ERROR ON SQL SERVER 2005:

ERROR ON SQL SERVER 2000:
(1 row(s) affected)
Server: Msg 245, Level 16, State 1, Procedure fnGenerateNewBoxId, Line 32
Syntax error converting the varchar value '*' to a column of data type int.
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TABLE:
CREATE TABLE [NewBoxId] (
      [ID] [int] IDENTITY (50290000, 1) NOT NULL ,
      [BoxId] [char] (20) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
      [ordernum] [varchar] (10) COLLATE SQL_Latin1_General_CP1_CI_AS NULL CONSTRAINT [DF_NewBoxId_ordernum] DEFAULT (1),
      [dateCreated] [datetime] NOT NULL CONSTRAINT [DF_NewBoxId_dateCreated] DEFAULT (getdate()),
      [used] [bit] NOT NULL CONSTRAINT [DF_NewBoxId_used] DEFAULT (0)
) ON [PRIMARY]
GO

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QUERY:
exec usp_GetBoxNumber 1234567

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STORED PROCEDURE
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_NULLS ON
GO
CREATE  PROCEDURE [dbo].[usp_GetBoxNumber]
@ord varchar(10)
as
declare @myIdentity int
insert into dbo.NewBoxID (ordernum, used) Values (@ord, 0)

select @myIdentity=SCOPE_IDENTITY()

update dbo.NewBoxID set Boxid = dbo.fnGenerateNewBoxId(@myIdentity)
where ID = @myIdentity
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FUNCTION:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE function [dbo].[fnGenerateNewBoxId]
(
@boxnumber int
)
Returns char(20)
as
Begin
      declare @fullstr as varchar(20)
      declare @checkdigit as varchar (20)
      declare @prefix as varchar(10)
      declare @work as varchar(20)
      declare @I as int
      declare @oddcounter as int
      declare @evencounter as int
      declare @cwork as int
      declare @oddtotal as int
      declare @eventotal as int
      declare @total as int

      set @oddcounter = 1
      set @evencounter = 2
      set @oddtotal = 0
      set @eventotal = 0
      set @prefix = '0000024964'
      set @work = RIGHT('000000000' + cast(@boxnumber as varchar(7)),9)
      set @fullstr = @prefix + @work
      set @I = len(@fullstr)

      while @oddcounter <= @I
      begin
            set @cwork = substring(@fullstr, @oddcounter, 1)
            --print @oddcounter
            --print @cwork
            set @oddtotal = @oddtotal + cast(@cwork as int)
            set @oddcounter = @oddcounter + 2

      end
      --select @oddtotal

      while @evencounter <= @I
            begin
                  set @cwork = substring(@fullstr, @evencounter, 1)
                  set @eventotal = @eventotal + cast(@cwork as int)
                  set @evencounter = @evencounter + 2
            end
      set @total = (@oddtotal * 3) + @eventotal
      set @cwork =  @total % 10
      if @cwork = 0
            begin
                  set @checkdigit = @cwork
            end
            else set @checkdigit = 10 - @cwork
      set @fullstr = @fullstr + @checkdigit
      Return(@fullstr)
End
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