Date comparison after format cdate

I have a linked csv table that contains a date in the format of Oct 2006 and my link spec brings it in as text.
This query works ok:
SELECT Format(CDate([Month]),"yy/mm") AS Expr1
FROM tblPCGoogleReport;

this query works ok:
SELECT Format(CDate([Month]),"yy/mm") AS Expr1
FROM tblPCGoogleSLXMatch INNER JOIN tblPCGoogleReport ON tblPCGoogleSLXMatch.[Google Account Name] = tblPCGoogleReport.Account
ORDER BY Format(CDate([Month]),"yy/mm");

this query errors with data type mismatch:
SELECT Format(CDate([Month]),"yy/mm") AS Expr1
FROM tblPCGoogleReport
ORDER BY Format(CDate([Month]),"yy/mm");

I don't understand why I get an error in the 3rd query...any ideas?