When booting the 3 ´recalcitrant´ distros in recovery mode , after
pressing ´resume normal ´ I get the normal display . However when again
booting in normal mode I don´t get any display,but in Ubuntu 12.04 coloured
areas/lines
But at least I can now try to find/install the appropriate Nvidia driver
possibly labelled ´nouveau´.
If the GT630 works with Mint 14 (12.10) it should also work with the 12.04
distros following ´normal boot´

This is the first ´quirky matter ´ with my 2 yrs old Intel i7 desktop
machine.