This is the output what happens now, when I try to watch tv via my notebook, which is the remote frontend, fglrx driver enabled. 
On my backend/frontend combo with mythbuntu 7.10 and the latest weekly builds and nvidia card everything is running fine. 

Frontend is still crashing, when I try to shut it down properly. You need the dump of it, tell me. 

2008-03-28 23:37:06.483 Using runtime prefix = /usr, libdir = /usr/lib
2008-03-28 23:37:06.969 XScreenSaver support enabled
2008-03-28 23:37:06.969 DPMS is active.
2008-03-28 23:37:06.988 Empty LocalHostName.
2008-03-28 23:37:06.988 Using localhost value of ubulap
2008-03-28 23:37:06.989 Testing network connectivity to 192.*.*.*
2008-03-28 23:37:07.207 New DB connection, total: 1
2008-03-28 23:37:12.440 Connected to database 'mythconverg' at host: 192.*.*.*
2008-03-28 23:37:12.443 Closing DB connection named 'DBManager0'
2008-03-28 23:37:12.443 Total desktop dim: 1280x800, with 1 screen[s].
2008-03-28 23:37:17.469 Connected to database 'mythconverg' at host: 192.*.*.*
2008-03-28 23:37:17.587 Using screen 0, 1280x800 at 0,0
2008-03-28 23:37:17.637 New DB connection, total: 2
2008-03-28 23:37:22.666 Connected to database 'mythconverg' at host: 192.*.*.*
2008-03-28 23:37:22.715 mythfrontend version: 0.21.20080304-1 www.mythtv.org
2008-03-28 23:37:22.715 Enabled verbose msgs:  important general
2008-03-28 23:37:23.593 Total desktop dim: 1280x800, with 1 screen[s].
2008-03-28 23:37:23.595 Using screen 0, 1280x800 at 0,0
2008-03-28 23:37:23.596 Switching to square mode (G.A.N.T)
2008-03-28 23:37:23.779 Using the Qt painter
mythtv: could not connect to socket
mythtv: No such file or directory
2008-03-28 23:37:23.779 lirc_init failed for mythtv, see preceding messages
2008-03-28 23:37:23.779 JoystickMenuClient Error: Joystick disabled - Failed to read /home/sven/.mythtv/joystickmenurc
2008-03-28 23:37:25.385 Loading from: /usr/share/mythtv/themes/G.A.N.T/base.xml
2008-03-28 23:37:25.522 Loading from: /usr/share/mythtv/themes/default/base.xml
2008-03-28 23:37:25.782 Registering Internal as a media playback plugin.
2008-03-28 23:37:36.602 Connecting to backend server: 192.*.*.*:6543 (try 1 of 5)
2008-03-28 23:37:36.604 Using protocol version 40
2008-03-28 23:37:36.645 TV: Attempting to change from None to WatchingLiveTV
2008-03-28 23:37:36.646 Using protocol version 40
2008-03-28 23:37:39.228 New DB connection, total: 3
2008-03-28 23:37:39.270 DPMS Deactivated 
2008-03-28 23:37:39.271 New DB connection, total: 4
2008-03-28 23:37:44.247 Connected to database 'mythconverg' at host: 192.*.*.*
2008-03-28 23:37:49.265 Connected to database 'mythconverg' at host: 192.*.*.*
2008-03-28 23:37:49.294 NVP: Disabling Audio, params(-1,2,44100)
2008-03-28 23:37:49.508 VideoOutputXv Error: Could not find suitable XVideo surface.
2008-03-28 23:37:49.508 VideoOutputXv: Falling back to X11 video output over a network socket.
			      *** May be very slow ***
2008-03-28 23:37:49.527 VideoOutputXv Error: XCreateImage failed: XJ_disp(0x8378820) visual(0x8378d60) 
                        XJ_depth(24) WxH(1280x800) bpl(3840)
2008-03-28 23:37:49.528 VideoOutputXv Error: Failed to create X buffers.
2008-03-28 23:37:49.872 Couldn't load deinterlace filter 
2008-03-28 23:37:49.892 OSD Theme Dimensions W: 640 H: 480
2008-03-28 23:37:50.416 TV: Changing from None to WatchingLiveTV
2008-03-28 23:37:50.419 Realtime priority would require SUID as root.
2008-03-28 23:37:50.557 OpenGLVideoSync()
2008-03-28 23:37:50.557 ~OpenGLVideoSync() -- begin
2008-03-28 23:37:50.557 ~OpenGLVideoSync() -- middle
2008-03-28 23:37:50.558 ~OpenGLVideoSync() -- end
2008-03-28 23:37:50.558 Video timing method: USleep with busy wait
2008-03-28 23:37:50.810 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 0 25
2008-03-28 23:37:50.812 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 28
2008-03-28 23:37:50.812 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 29
2008-03-28 23:37:50.812 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 0 30
2008-03-28 23:37:50.814 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 31
2008-03-28 23:37:50.815 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 32
2008-03-28 23:37:50.815 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 33
2008-03-28 23:37:50.815 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 34
2008-03-28 23:37:50.815 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 35
2008-03-28 23:37:50.815 [mpeg2video @ 0xb73e7ac8]Warning MVs not available
2008-03-28 23:37:51.108 VideoOutputXv Error: Could not find suitable XVideo surface.
2008-03-28 23:37:51.109 VideoOutputXv: Falling back to X11 video output over a network socket.
			      *** May be very slow ***
2008-03-28 23:37:51.109 VideoOutputXv Error: XCreateImage failed: XJ_disp(0x8378820) visual(0x8378d60) 
                        XJ_depth(24) WxH(1280x800) bpl(3840)
2008-03-28 23:37:51.109 VideoOutputXv Error: Failed to create X buffers.
2008-03-28 23:37:51.527 AFD: Opened codec 0x9e3ad90, id(MPEG2VIDEO) type(Video)
2008-03-28 23:37:51.527 AFD: codec MP3 has 2 channels
2008-03-28 23:37:51.527 AFD: Opened codec 0x9e3b110, id(MP3) type(Audio)
2008-03-28 23:37:51.601 Opening audio device 'default'. ch 2(2) sr 48000
2008-03-28 23:37:51.601 Opening ALSA audio device 'default'.
ALSA lib pcm_dmix.c:874:(snd_pcm_dmix_open) unable to open slave
2008-03-28 23:37:51.608 AudioOutput Error: snd_pcm_open(default): Device or resource busy
2008-03-28 23:37:51.608 NVP: Disabling Audio, reason is: snd_pcm_open(default): Device or resource busy
2008-03-28 23:37:51.695 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 0 25
2008-03-28 23:37:51.696 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 28
2008-03-28 23:37:51.696 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 29
2008-03-28 23:37:51.696 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 0 30
2008-03-28 23:37:51.696 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 31
2008-03-28 23:37:51.696 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 32
2008-03-28 23:37:51.696 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 33
2008-03-28 23:37:51.696 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 34
2008-03-28 23:37:51.696 [mpeg2video @ 0xb73e7ac8]invalid mb type in I Frame at 0 35
2008-03-28 23:37:51.696 [mpeg2video @ 0xb73e7ac8]Warning MVs not available
2008-03-28 23:37:51.754 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 11 26
2008-03-28 23:37:51.754 [mpeg2video @ 0xb73e7ac8]skipped MB in I frame at 3 7
2008-03-28 23:37:51.754 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 0 8
2008-03-28 23:37:51.754 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 0 9
2008-03-28 23:37:51.755 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 1 10
2008-03-28 23:37:51.755 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 0 11
2008-03-28 23:37:51.755 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 0 12
2008-03-28 23:37:51.755 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 0 13
2008-03-28 23:37:51.755 [mpeg2video @ 0xb73e7ac8]skipped MB in I frame at 4 14
2008-03-28 23:37:51.755 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 1 15
2008-03-28 23:37:51.755 [mpeg2video @ 0xb73e7ac8]skipped MB in I frame at 5 16
2008-03-28 23:37:51.755 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 0 17
2008-03-28 23:37:51.755 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 0 18
2008-03-28 23:37:51.755 [mpeg2video @ 0xb73e7ac8]ac-tex damaged at 0 19
2008-03-28 23:37:51.757 [mpeg2video @ 0xb73e7ac8]Warning MVs not available
2008-03-28 23:39:04.005 AFD: Opened codec 0x92e6880, id(MPEG2VIDEO) type(Video)
2008-03-28 23:39:04.005 AFD: codec MP3 has 2 channels
2008-03-28 23:39:04.006 AFD: Opened codec 0x9fa4e90, id(MP3) type(Audio)
2008-03-28 23:39:04.006 AFD: codec MP3 has 2 channels
2008-03-28 23:39:04.006 AFD: Opened codec 0x92def10, id(MP3) type(Audio)
2008-03-28 23:39:04.193 Opening audio device 'default'. ch 2(2) sr 48000
2008-03-28 23:39:04.194 Opening ALSA audio device 'default'.
ALSA lib pcm_dmix.c:874:(snd_pcm_dmix_open) unable to open slave
2008-03-28 23:39:04.198 AudioOutput Error: snd_pcm_open(default): Device or resource busy
2008-03-28 23:39:04.198 NVP: Disabling Audio, reason is: snd_pcm_open(default): Device or resource busy
2008-03-28 23:39:23.076 NVP: Prebuffer wait timed out 10 times.
2008-03-28 23:39:24.682 NVP: Prebuffer wait timed out 10 times.
2008-03-28 23:39:24.689 AFD: Opened codec 0x92d9080, id(MPEG2VIDEO) type(Video)
2008-03-28 23:39:24.689 AFD: codec MP3 has 2 channels
2008-03-28 23:39:24.689 AFD: Opened codec 0x933e280, id(MP3) type(Audio)
2008-03-28 23:39:24.689 AFD: codec MP3 has 1 channels
2008-03-28 23:39:24.689 AFD: Opened codec 0x9323a40, id(MP3) type(Audio)
2008-03-28 23:39:24.689 AFD: codec AC3 has 2 channels
2008-03-28 23:39:24.691 AFD: Opened codec 0x9fc2fd0, id(AC3) type(Audio)
2008-03-28 23:39:24.741 AFD: Opened codec 0xa0d7a10, id(DVB_SUBTITLE) type(Subtitle)
2008-03-28 23:39:24.822 Opening audio device 'default'. ch 2(2) sr 48000
2008-03-28 23:39:24.822 Opening ALSA audio device 'default'.
ALSA lib pcm_dmix.c:874:(snd_pcm_dmix_open) unable to open slave
2008-03-28 23:39:24.824 AudioOutput Error: snd_pcm_open(default): Device or resource busy
2008-03-28 23:39:24.825 NVP: Disabling Audio, reason is: snd_pcm_open(default): Device or resource busy
2008-03-28 23:39:29.952 TV: Attempting to change from WatchingLiveTV to None
2008-03-28 23:39:30.353 TV: Changing from WatchingLiveTV to None
2008-03-28 23:39:30.375 DPMS Reactivated.
Segmentation fault (core dumped)