Video Card Problems!?

My video card is a XFX Radeon HD 6670. I have a gigabyte ga-78lmt-s2p motherboard. If i install the video card and dont plug in my monitor directly to the video card, nothing will display on the monitor. If I plug into directly into the video card I can access the bios but if i try to boot i get a flickering screen of purple (since im running ubuntu 64bit) and it wont boot. If i dont install the video card everything works and boots. Please help!|||from the sound of it i think the video card is bad i don't use ati on my linux pc but lotz do so it should have the kernel extensions in it have u checked if the card is working on any other pc's|||try different drivers for the graphics card. also tried on another window pc see if it worked there.