I have te same problem.
X doesn't run both live or installer mode.
I installed in text mode, checked the drivers but don't work.
In the text mode installation you don't have the choice "manual partitioning", so I prepared a ext3 partition before the installation and the I chose the option "use the linux partition".
This is very weird. Why there's no "manual partitioning"??
The Nvidia driver are correctly installed. Apparently.
My HP pavilion is 6 yars old. I use sabayon there since the 3.5.
I know the issues I can have with the Nvidia drivers. Issues happens if I don't install the proper driver, i.e. nvidia-drivers-97, but this isn't my case.
This is the output.
There was a 5.1 gnome perfectly working on this pc, but past week the HD broke and I replaced. Now I've a new HD, bigger, but sabayon works only in text mode