Peter.

Normally, in setuproutines in just at the start of the program
I am set the SPCR to

MOV SPCR,#0DDh

It's the common state.
But in case of using the 3100, I have to change CPOL and
CPHA. I dont think the change CPHA i nessesary.

MOV SPCR,#0D1h

What I did there, I was inverted the SPI-CLK.
After that changing - as you know, the uP are running a several
of instructions after programmer-reset, before it will start programming,
and then you blow your chance.
It was a smart way to fool the uP, that you jump immidiatley
to INT by tie the EX0 or EX1 to gnd.
As I have implemented now when I am develop the soft,
I have a wait-loop for at least 500mS before all setup.

I have followd the board-discussion abt this problems, and
perhaps, Peter, the reason why you not have discover this
problems, might be that you use an another programmer,
which is faster to grab the programming mode.
I am not shure, but I have an weak memory of that you told
someone here that you built your own programmer.!?