Hi,
Next step was to reboot into the install kernel again and try adding the extra sets. This time comp was extracted without error but the next set, man, threw 'invalid header', data stream error', 'unexpected EOF and failed. This suggests that sysinst is running out of some resource, possibly RAM, when asked to extract multiple sets.
If the system were running out of some resource, it would fail to launch new processes or kill off running processes - it wouldn't randomly fail.
There's a possibility that there's something wrong with the install kernel. If you install and boot into a really basic install, then untargzip additional sets, does that work?
John