急救，ubuntu无法启动（不能正确显示输入用户名的界面）

[lucky_pig]

我是ubuntu新手，刚装utuntu半个月，前一段时间ubuntu启动都是好好的，就是昨天启动到输入用户名和密码的界面时，那界面只是一系列的竖形彩色条纹，没有漂亮的ubuntu黄色输入界面，鼠标也没反应。然后我从recovery模式启动，用命令dpkg-reconfigure -phigh xserver -xorg把xorg.conf更新了一下，再启动，这样有时候可以正常启动到输入用户名和密码的界面，有时候又不可以，不知道是为什么，我已经搞了好多次了，还是靠概率来启动，估计过几天就完全不能启动了，大家帮帮忙阿，现谢谢了！
对了，我的/etc/X11/xor.conf文件内容如下：
# xorg.conf (xorg X Window System server configuration file)
#
# This file was generated by dexconf, the Debian X Configuration tool, using
# values from the debconf database.
#
# Edit this file with caution, and see the xorg.conf manual page.
# (Type "man xorg.conf" at the shell prompt.)
#
# This file is automatically updated on xserver-xorg package upgrades *only*
# if it has not been modified since the last upgrade of the xserver-xorg
# package.
#
# If you have edited this file but would like it to be automatically updated
# again, run the following command:
# sudo dpkg-reconfigure -phigh xserver-xorg

Section "Files"
EndSection

Section "InputDevice"
Identifier "Generic Keyboard"
Driver "kbd"
Option "CoreKeyboard"
Option "XkbRules" "xorg"
Option "XkbModel" "pc105"
Option "XkbLayout" "us"
EndSection

Section "InputDevice"
Identifier "Configured Mouse"
Driver "mouse"
Option "CorePointer"
Option "Device" "/dev/input/mice"
Option "Protocol" "ImPS/2"
Option "ZAxisMapping" "4 5"
Option "Emulate3Buttons" "true"
EndSection

Section "InputDevice"
Driver "wacom"
Identifier "stylus"
Option "Device" "/dev/input/wacom"
Option "Type" "stylus"
Option "ForceDevice" "ISDV4" # Tablet PC ONLY
EndSection

Section "InputDevice"
Driver "wacom"
Identifier "eraser"
Option "Device" "/dev/input/wacom"
Option "Type" "eraser"
Option "ForceDevice" "ISDV4" # Tablet PC ONLY
EndSection

Section "InputDevice"
Driver "wacom"
Identifier "cursor"
Option "Device" "/dev/input/wacom"
Option "Type" "cursor"
Option "ForceDevice" "ISDV4" # Tablet PC ONLY
EndSection

Section "Device"
Identifier "Intel Corporation 82845G/GL[Brookdale-G]/GE Chipset Integrated Graphics Device"
Driver "intel"
BusID "PCI:0:2:0"
EndSection

Section "Monitor"
Identifier "M150"
Option "DPMS"
Option "Enable"
EndSection


Section "Screen"
Identifier "Default Screen"
Device "Intel Corporation 82845G/GL[Brookdale-G]/GE Chipset Integrated Graphics Device"
Monitor "M150"
DefaultDepth 24
SubSection "Display"
Modes "1024x768" "832x624" "800x600" "720x400" "640x480"
EndSubSection
EndSection

Section "ServerLayout"
Identifier "Default Layout"
Screen "Default Screen"
InputDevice "Generic Keyboard"
InputDevice "Configured Mouse"

# Uncomment if you have a wacom tablet
# InputDevice "stylus" "SendCoreEvents"
# InputDevice "cursor" "SendCoreEvents"
# InputDevice "eraser" "SendCoreEvents"
EndSection

不知道是不是这个文件问题
在线等......