new install of 12.04 on an old dell with a radeon ATI RV516 video card with monitor out and s-video out.

During boot up all is good. Both screens operate and look fine. Then just before the desktop appears the cCRT goes purple and is covered in heavy horizontal lines, but as i said during boot up it was fine and the resolution was fine. The main monitor, an lcd, operates normally.

everything else works fine, it's just the picture on the CRT that is screwed up.

I used the same monitor and CRT running 11.10 which worked fine

any help would be appreciated and yes i am a newbie to ubuntu here is a vid showing the completely normal screens at reboot then the purple badness when the desktop loads ?? and don't laugh at the slow machine, it's old. http://www.youtube.com/my_videos_edit?ns=1&video_id=zfuh6lBMLnc