>>As stated before in this thread, this is NOT a bug. From help on Alter table:
>>
>>ALTER TABLE might not produce consistent results when used with Visual FoxPro cursors created by the CREATE CURSOR command. In particular, you can create a Visual FoxPro cursor with features, such as long field names, that are normally available only with tables...>
>
>Pretext explanation. If long field name doesn't supported for cursors VFP should give an error "You cannot use long field names with cursors". That would be clearly.
>
>VFP behaviour strange with this issue. gives different unrelative erros with different conditions...
>
>It's a bug for me.

You can in deed use long field names in cursors, but you can not alter the structure of a cursor which has long field names. This is documented, and thus not a bug.