If he's using AVRISP MkII then I agree, the -i option is unlikely to work. The AVRISP spec says that the SCLK frequency can go down to 50Hz, but maybe avrdude can't adjust it, or has limited range?
It might be better to use the AVR Studio interface instead, because that provides direct control of the frequency according to the manual at http://www.atmel.com/Images/avrispmkii_ug.pdf.