There is an additional detail here some may not be aware of
some versions of the FX5200 hardware, miss-report their abilities to the xserver - this causes graphics corruption and lock up, I would look to using the video=vesa in place of the vga=788 entry, (or trying the fbdev boot)
I suspect its the FX5200 that needs to be set up correctly (manually) I have 5 of these cards of which 3 are effected by garbled/freezing graphics.
I would be tempted to install initially without the pci-Nvidia card then when installed, adding in the nvidia card, booting into run-level 3 to set the card up then rebooting with the pci card as the primary video source.
If your's is one of the cards effected then is a hardware issue that has work arounds - I willsee if i can locate them incase