Exporting Schema DDL

Hi !

I am trying to export a schema DDL from Toad and I get ORA-01795 error:

maximum number of expressions in a list is 1000
Cause: More than 254 columns or expressions were specified in a list.
Action: Remove some of the expressions from the list.

Any idea ?
I am using Toad for Oracle Base, version
The database is Oracle 10g Express.

Thanks !