Erni:
Maybe you need the updated version mentioned in this thread:
I used the current version (15) which should work as well, shouldn't it? But I switched back to http://hlt.media.mit.edu/?p=1695 after it didn't work.
MontySylver:
I used an ATTiny85 to send serial data and an Arduino Uno to receive it. First I got some strange gibberish too until I pulled the ATTiny's VCC out by accident. Without VCC on the ATTiny it sent what I wanted, after reconnecting VCC it was gibberish again. There were no pins except Tx, Rx and GND connected.
Not sure how this is supposed to work without power but just to test everything I tried it as well and the AtTiny stopped transmitting after pulling out the VCC cable.