Conversion failed when converting from a character string to uniqueidentifier error in SQL Server

I've been getting the error "Conversion failed when converting from a character string to uniqueidentifier" and am finally at the end of my rope. I've narrowed down my problem to as small as possible while keeping the error in tact. Install the CSV splitter from here first if you want to reproduce:

http://www.sqlservercentral.com/articles/Tally+Table/72993/

Here's the test code. I'm on SQL 2008R2 but in a database that is SQL 2005 compatible:

IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[ZZZTESTTABLE]') AND type in (N'U'))
DROP TABLE [dbo].[ZZZTESTTABLE]
GO

CREATE TABLE [dbo].[ZZZTESTTABLE](
    [Col1] [uniqueidentifier] NOT NULL,
 CONSTRAINT [PK_ZZZTESTTABLE] PRIMARY KEY CLUSTERED 
(
    [Col1] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

-- Test table that I would like to check my values against
insert dbo.ZZZTESTTABLE(Col1) values('85B049B7-CDD0-4995-B582-5A74523039C0')

-- Test string that will be split into table in the DelimitedSplit8k function
declare @temp varchar(max) = '918E809E-EA7A-44B5-B230-776C42594D91,6F8DBB54-5159-4C22-9B0A-7842464360A5'

-- I'm trying to delete all data in the ZZZTESTTABLE that is not in my string but I get the error 
delete dbo.ZZZTESTTABLE
where Col1 not in 
(
-- ERROR OCCURS HERE
    select cast(Item as uniqueidentifier) from dbo.DelimitedSplit8K(@temp, ',')
)

HERE's the source for the DelimitedSplit8K function so you don't have to go and find it:

CREATE FUNCTION dbo.DelimitedSplit8K
--===== Define I/O parameters
        (@pString VARCHAR(8000), @pDelimiter CHAR(1))
RETURNS TABLE WITH SCHEMABINDING AS
 RETURN
--===== "Inline" CTE Driven "Tally Table" produces values from 0 up to 10,000...
     -- enough to cover VARCHAR(8000)
  WIT