Avrdude error with Leonardo ISP

Hi!
I get your same error trying to upload a sketch into an attiny2313 through an Arduino Leonardo...it's about a week that I'm trying to solve this problem!
Initially I tought that there was a problem with the attiny, wrongly configured/initialized, but yesterday I try the same procedure reported here How-To: Shrinkify Your Arduino Projects - Make: on my friend Arduino Duemilanove and it worked smoothly.

Moreover I tried to bypass the IDE and use avrdude on shell with the following command:

avrdude -p attiny2313 -c arduino -P com17

obtaining:

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.03s

avrdude: Device signature = 0xffffff
avrdude: Yikes!  Invalid device signature.
         Double check connections and try again, or use -F to override
         this check.

avrdude done.  Thank you.

It is the same result obtained if the pins from the Arduino are not connected to the attiny, but they are!

So there is something wrong using the Leonardo, maybe some pin mapping is changed or there is a paritucular baudrate to use.
I tried also to change some values in the avrduce.conf file and use directly the icsp pins from the arduino obtaining always same error.

I hope that someone more expert can help us with this unsolved problem :-s

Best Regards