X reboot when trying to watch tv

[yawie]

Hello all,
I just (i spent my day to though!) installed mythtv 0.19. (svn, then ./configure, gmake, make make install). (I had previously the ubuntu package for mythtv 0.1

I ran the setup, sounded quite nice, found some channels, I changed the channel detected to make it match the xml guide.

The issue now :
When I watch TV, X immediatly restart or crash
the very odd thing is that I can record a show, look at the preview bu if I try to watch the recorded show fullscreen it chrashes.

Do you have any idea where I can look ? (or better, to solve the problem).

I have an ahtlon x2 with smp 2.6.15-22 ubuntu smp kernel
nvidia restricted drivers
a bt 878 hapauge card
(the card seems to works, but I can't make xawtv work

WARNING: Your X-Server has no DGA support.
WARNING: couldn't find framebuffer base address, try manual
         configuration ("v4l-conf -a <addr>")

scantv works

Thanks for your answers