CASE Statement Error: Cannot Convert A Char Value To Money

I am trying to write a Procedure in SQL 2005 that retreives a list of rows from the database. I pass to the procedure sorting parameters. This procedure works fine for all of the fields that I enter in the Order By, except for one.
The field that does not work is a varchar(500) field (named Description).
I am not sure what the problem is.
The error that I am getting is:

Msg 235, Level 16, State 0, Line 13

Cannot convert a char value to money. The char value has incorrect syntax.

Attached is the T-SQL Code. The declare and set statements in the beginning are for informational purposes.
Any help is appreciated.
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declare @Match varchar(75)

declare @NumRows int

declare @StartPos int

declare @OrderBy varchar(25)

declare @OrderDir varchar(4)


set @Match = 'dog% AND bark%'

set @NumRows = 25

set @StartPos = 100

set @OrderBy = 'Description'

set @OrderDir = 'ASC'


WITH catitems AS

(

SELECT ci.ID, ci.SupplierCode, ci.Description, ci.AUDIO_LINK, ci.SoundLength, ci.HighCost, ci.Channels,

ROW_NUMBER() OVER (ORDER BY

CASE

WHEN @OrderBy='ID' AND @OrderDir='ASC'

THEN CAST(ci.ID AS int)

WHEN @OrderBy='SupplierCode' AND @OrderDir='ASC'

THEN CAST(ci.SupplierCode As int)

WHEN @OrderBy='Description' AND @OrderDir='ASC'

THEN CAST(ci.[Description] As varchar(500))

WHEN @OrderBy='HighCost' AND @OrderDir='ASC'

THEN CAST(ci.HighCost AS money)

WHEN @OrderBy='Channels' AND @OrderDir='ASC'

THEN CAST(ci.Channels AS smallint)

END ASC,

CASE

WHEN @OrderBy='ID' AND @OrderDir='DESC'

THEN CAST(ci.ID AS int)

WHEN @OrderBy='SupplierCode' AND @OrderDir='DESC'

THEN CAST(ci.SupplierCode As int)

WHEN @OrderBy='Description' AND @OrderDir='DESC'

THEN CAST(ci.[Description] As varchar(500))

WHEN @OrderBy='HighCost' AND @OrderDir='DESC'

THEN CAST(ci.HighCost AS money)

WHEN @OrderBy='Channels' AND @OrderDir='DESC'

THEN CAST(ci.Channels AS smallint)

END DESC) As RowNo

FROM TableName As ci

WHERE CONTAINS (ci.Keywords, @Match) AND ShowOnWeb=1

)

SELECT catitems.ID,

catitems.SupplierCode,

catitems.Description,

catitems.AUDIO_LINK,

catitems.HighCost,

catitems.Channels

FROM catitems

WHERE RowNo BETWEEN @StartPos AND @StartPos + @NumRows -1
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Thanks,

Aric