Display failing for text sessions and shutdown in Linux, start/GUI (and Windows) fine

Hello,

When I try to open a text session in Linux (CTRL-Alt-F1, for example), the display goes all weird -- it starts slowly morphing into blotches and lines, and is not usable until I press CTRL-ALT-F7 again to return to the GUI (and then it instantly refreshes and reverts to the login screen).
Then when I shut it down, it does the same thing (morphing into a mainly black screen through creepy whitish blotches).

I have attached pictures of the startup screen and the GUI (both fine), and several stages of the display morphing from the GUI to a blackish screen (1 to 3 in chronological order), and the shutdown screen.

When using windows, no problem at all.

I have no idea what is going on, would anyone have a clue??

My computer is a VAIO VGN-S4XP. Hadn't used it in a long time (more than a year). I dimly remember installing Kubuntu over my Mandriva and being disappointed, but I had not used linux much after that, so I am not sure I had checked the terminal sessions before.

Thank you for your help!