My experience is that to connect to OS 10.4 or later from a pre-OS 9 machine you need to have Shareway IP installed in the OS 7 and 8 machines. Shareway IP is available from Open Door Networks for about $39. Apple added the Shareway IP code to System 9, so that's why the 9.2.2 system connects okay. Open Door Networks is at http://www.opendoor.com.

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Good luck.