Perhaps keep the G5 turned off while you fix the Mini.
Is there something strange about Minis mounting disks? - See:
Does it mount if you don't use wireless?
Does repairing the Mini disk and permissions change anything?
All seems to be ok with HD... mounted directly without problem.
The difference between two macs is in the Belkin icon on the menu bar,
on the G5 still blue and on the mini is forever gray...like a kind of 'no connections' or 'inactive',
but internet is ok...let me see if Belkin site can help...
Thank you for your help.