SoftwareSerial with ATTiny84 using ATtiny library

Erni:
So I added #include "print.h" in the WProgram.h , and now it compiles and uploads.

Excellent.

I was thinking it maybe had something to do with the clock speed which was 128kHz,

The minimum supported clock speed is 1 MHz. If I can remember, I'll put a check in the header file.

so I tried at 9,6 mHz and got this error:

--- Knock-Bang fault: 11 ---
i get the correct respons from the serial monitor, when I use @,# and !

fault_timeout_knock ... In the interrupt service routine, a knock was not detected within the time limit.

Other then a wire, is anything connected to MISO?

Try adding a 10K or 4.7K or 1K pullup resistor to MISO. And/or, if the wire on MISO connecting the programmer to the target is longish, try a shorter and/or fatter wire.