It seems your DB API adapter (kinterbasedb) returned unicode values.
StringCol tried to encode them to strings in dbEncoding (ascii) and
failed. Perhaps you have to set a proper dbEncoding. SQLObject 1.1 can
set one encoding per table or per connection.

Hmmm... the unicode type string comes from the TurboGears web form actually.
Now I am encoding it to the utf-8 str type when it comes from the web form but the Error occurs as before

  File "/usr/lib/python2.5/site-packages/SQLObject-0.10.1-py2.5.egg/sqlobject/firebird/", line 105, in _queryInsertID
    q = self._insertSQL(table, names, values)
  File "/usr/lib/python2.5/site-packages/SQLObject-0.10.1-py2.5.egg/sqlobject/", line 387, in _insertSQL
    ', '.join([self.sqlrepr(v) for v in values])))
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 16: ordinal not in range(128)

I made the change in the sqlobject.dburi from

but nothing changed.

I made the change in the table column definition. Because I am using "fromDatabase = True" for all tables,  I added the manual definition of the column in the table definition:
poznamka = UnicodeCol(dbEncoding = "utf8")

but nothing changed.

Do you have any idea how to force SQLObject to use the utf-8 instead of "ascii" for decoding?