In the Create new user window in the schema browser, there's an option, "Set Tablespace as defaults for all User creates". When this is checked it will carry over the default tablespace name and temp tablespace name for subsequent New User creates. This even carries over to other entirely different database connections in Toad; however the same tablespace names do not exist in other database connections; thus Toad will generate a bad statement to create tablespaces that do not exist.
WORKAROUND:
Uncheck the option "Set Tablespace as defaults for all User creates" in the create user window.
STATUS:
Waiting for a fix in a future release of Toad for Oracle.
