ERROR: Arithmetic overflow error converting float to data type numeric
The error seems to indicate that the DECIMAL datatype is not defined with the correct precision and scale. The default is DECIMAL(18,0), but something may have happened with your defaults? When I run the query below as you have (just changed to a table variable and added the precision and scale), I am not receiving any error.

DECLARE @test TABLE
([Parcel Number 2(max)] FLOAT)

INSERT INTO @test
        ( [Parcel Number 2(max)] )
VALUES  ( '1.4515020001e+012'  -- Parcel Number 2(max) - float
          )

SELECT CAST(CAST(CAST([Parcel Number 2(max)] AS FLOAT) AS DECIMAL(18,0)) AS NVARCHAR(255))
FROM @test WHERE [Parcel Number 2(max)] = '1.4515020001e+012'


As an FYI, I do get an arithmetic overflow if I try DECIMAL(12,0).