[NTLK] Cannot install NCU on Mac OS 9

[r0]

Hi there,

I'm running 9.2.2 on a iMac G3 DV+ and I just received a serial cable 
and a Keyspan USA-28X.

I can't manage to install NCU on that machine : the installer gets stuck 
at "Preparing to install..", and nothing happens, besides the cursor 
spinning.
Trying to kill the installer locks the Finder with another installer 
process, and trying to kill it spawns MacsBug continously.

Is this normal? Should I use another software to communicate with the 
Newton?

Thanks for your help.