Try to search Installshield KB at
http://support.installshield.com/default.asp#kb for this error.
>Hints on what I'm doing wrong to get his error message?
>
>ISEXP : error -6264: A record in the Property table is using string ID 'ID_STRING1' for column 'Value' but this string is blank and the column is not nullable>
>
>
--sb--