Bizarre error "a character string failed conversion to a numeric value"

Database

Bizarre error "a character string failed conversion to a numeric value"

Hi,

   I coldn't figure out why this query would fail on my 13.10.04 instance, it seems teradata db has a problem with type checking in a derived table.

This works

select count(case  when W_AREA_CODE in ('Authorization Request', 'Referral Request') then ROW_WID end) from W_SRVREQ_D

but this with a reprojection fails with code 3535 A character string failed conversion to a numeric value

 select

     T1.c1 as c1

from

     ( select count(case  when W_AREA_CODE in ('Authorization Request', 'Referral Request') then ROW_WID end)  as c1 from W_SRVREQ_D

     ) T1

any help is much appreicated