I have the same issue here on a HP/Compaq D510 SFF computer (business model). Things worked fine in Ubuntu Hardy but after an upgrade to Intrepid in August, X broke, and is still broken. I'm running 2.6.27-3 with and xserver-xorg-video-intel 2:2.4.1-1ubuntu4 My display manager is KDM. Whenever I try to login to KDE4 the screen goes black after the first KDE icon (during startup) appears during KDE initialization. If I enable desktop effects in Gnome, X also dies. Restarting X or KDM doesn't help either, I need to reboot the computer. My Xorg0.log is full of: (EE) intel(0): underrun on pipe A! The last entries in Xorg.0.log before things go crazy are these: (II) Initializing built-in extension XEVIE (II) AIGLX: Screen 0 is not DRI2 capable drmOpenDevice: node name is /dev/dri/card0 drmOpenDevice: open result is 11, (OK) drmOpenByBusid: Searching for BusID pci:0000:00:02.0 drmOpenDevice: node name is /dev/dri/card0 drmOpenDevice: open result is 11, (OK) drmOpenByBusid: drmOpenMinor returns 11 drmOpenByBusid: drmGetBusid reports pci:0000:00:02.0 (II) AIGLX: enabled GLX_MESA_copy_sub_buffer (II) AIGLX: enabled GLX_SGI_swap_control and GLX_MESA_swap_control (II) AIGLX: enabled GLX_texture_from_pixmap with driver support (II) AIGLX: Loaded and initialized /usr/lib/dri/i915_dri.so (II) GLX: Initialized DRI GL provider for screen 0 (II) intel(0): Setting screen physical size to 338 x 270 (EE) intel(0): underrun on pipe A! (II) config/hal: Adding input device Microsoft Microsoft 5-Button Mouse with IntelliEye(TM) (II) LoadModule: "evdev" (II) Loading /usr/lib/xorg/modules/input//evdev_drv.so (II) Module evdev: vendor="X.Org Foundation" compiled for 1.5.0, module version = 2.0.99 Module class: X.Org XInput Driver ABI class: X.Org XInput driver, version 2.1 (**) Microsoft Microsoft 5-Button Mouse with IntelliEye(TM): always reports core events (**) Microsoft Microsoft 5-Button Mouse with IntelliEye(TM): Device: "/dev/input/event3" (II) Microsoft Microsoft 5-Button Mouse with IntelliEye(TM): Found x and y relative axes (II) Microsoft Microsoft 5-Button Mouse with IntelliEye(TM): Found 5 mouse buttons (II) Microsoft Microsoft 5-Button Mouse with IntelliEye(TM): Configuring as mouse (II) XINPUT: Adding extended input device "Microsoft Microsoft 5-Button Mouse with IntelliEye(TM)" (type: MOUSE) (**) Microsoft Microsoft 5-Button Mouse with IntelliEye(TM): YAxisMapping: buttons 4 and 5 (**) Microsoft Microsoft 5-Button Mouse with IntelliEye(TM): EmulateWheelButton: 4, EmulateWheelInertia: 10, EmulateWheelTimeout: 200 (II) config/hal: Adding input device Apple, Inc Apple Keyboard (**) Apple, Inc Apple Keyboard: always reports core events (**) Apple, Inc Apple Keyboard: Device: "/dev/input/event2" (II) Apple, Inc Apple Keyboard: Found keys (II) Apple, Inc Apple Keyboard: Configuring as keyboard (II) XINPUT: Adding extended input device "Apple, Inc Apple Keyboard" (type: KEYBOARD) (**) Option "xkb_rules" "evdev" (**) Apple, Inc Apple Keyboard: xkb_rules: "evdev" (**) Option "xkb_model" "pc105" (**) Apple, Inc Apple Keyboard: xkb_model: "pc105" (**) Option "xkb_layout" "se" (**) Apple, Inc Apple Keyboard: xkb_layout: "se" (**) Option "xkb_options" "lv3:ralt_switch" (**) Apple, Inc Apple Keyboard: xkb_options: "lv3:ralt_switch" (II) config/hal: Adding input device Apple, Inc Apple Keyboard (**) Apple, Inc Apple Keyboard: always reports core events (**) Apple, Inc Apple Keyboard: Device: "/dev/input/event1" (II) Apple, Inc Apple Keyboard: Found keys (II) Apple, Inc Apple Keyboard: Configuring as keyboard (II) XINPUT: Adding extended input device "Apple, Inc Apple Keyboard" (type: KEYBOARD) (**) Option "xkb_rules" "evdev" (**) Apple, Inc Apple Keyboard: xkb_rules: "evdev" (**) Option "xkb_model" "pc105" (**) Apple, Inc Apple Keyboard: xkb_model: "pc105" (**) Option "xkb_layout" "se" (**) Apple, Inc Apple Keyboard: xkb_layout: "se" (**) Option "xkb_options" "lv3:ralt_switch" (**) Apple, Inc Apple Keyboard: xkb_options: "lv3:ralt_switch" (II) config/hal: Adding input device Macintosh mouse button emulation (**) Macintosh mouse button emulation: always reports core events (**) Macintosh mouse button emulation: Device: "/dev/input/event0" (II) Macintosh mouse button emulation: Found x and y relative axes (II) Macintosh mouse button emulation: Found 3 mouse buttons (II) Macintosh mouse button emulation: Configuring as mouse (II) XINPUT: Adding extended input device "Macintosh mouse button emulation" (type: MOUSE) (**) Macintosh mouse button emulation: YAxisMapping: buttons 4 and 5 (**) Macintosh mouse button emulation: EmulateWheelButton: 4, EmulateWheelInertia: 10, EmulateWheelTimeout: 200 (EE) intel(0): underrun on pipe A! (EE) intel(0): underrun on pipe A! ... 00:00.0 Host bridge [0600]: Intel Corporation 82845G/GL[Brookdale-G]/GE/PE DRAM Controller/Host-Hub Interface [8086:2560] (rev 01) Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx- Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- SERR- Kernel driver in use: agpgart-intel Kernel modules: intel-agp 00:02.0 VGA compatible controller [0300]: Intel Corporation 82845G/GL[Brookdale-G]/GE Chipset Integrated Graphics Device [8086:2562] (rev 01) Subsystem: Compaq Computer Corporation Device [0e11:00b9] Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx- Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- SERR-