CTE Error (nvarchar to numeric)

I'm using a CTE to convert SSRS stored proc's into BO stored proc's, as apparently I can't use temp tables with Business Objects.

I'm having this query:

;WITH cte1AS(     SELECT  cv.issue            , cv.customfield            , CAST(STRINGVALUE AS NUMERIC) AS priority_num      --INTO    #temp_priority_val      FROM    proddb1.customfieldvalue cv WITH (NOLOCK)              INNER JOIN proddb1.customfield e WITH (NOLOCK)                 ON  cv.CUSTOMFIELD = e.id                  AND e.cfname = 'Issue Priority')  ,cte2AS(     SELECT  a.ISSUE            , f.customvalue priority_num      --INTO    #temp_priority      FROM    cte1 a             INNER JOIN proddb1.customfieldoption f WITH (NOLOCK)                 ON  a.CUSTOMFIELD = f.CUSTOMFIELD                         AND CAST(a.priority_num AS NUMERIC) = f.id) SELECT * FROM cte2 

I keep getting an Error converting data type nvarchar to numeric. error on this execution. The priority_num column is an nvarchar column that is CAST in the first CTE. When I execute this within the original statement that had the temp tables it works perfectly fine. It must be something with the CTE scope?