原来有很多人有这样的问题阿，这个问题主要是在笔记本用户上出现的。基本确实是和无线网卡有关系，这个东西到处惹火，在vista里面我也吃了不少的苦。
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/355054
另外ubuntuforums论坛上有人给出了一个解决方案，想应用了试一下。
Re: cannot shutdown / reboot laptop on 9.04
was having the same problem. If the laptop’s wireless card was “on” at
shutdown, it would hang and I’d get that blinking cursor in the top
left corner. If the laptop’s wireless card was “off” at shutdown, no
problems at all.
So here’s how I fixed it …
Abstract: Add a short script to the init.d directory that uses
“modprobe -r” to remove the wireless driver. Then add symbolic links to
that script in both rc0.d and rc6.d directories.
Details:
1. Open a terminal and become super-user (yeah, this is a bad security
practice, but I’m too lazy to type sudo before everything).
su
2. Navigate to the init.d directory.
cd /etc/init.d
3. Touch and edit your new wireless shutdown script. I use “vi,” but feel free to use “gedit” if you like.
vi killwlan
4. Add line(s) that “modprobe -r” your wireless driver module(s).
In MY case, I remove both “ipw3945” and “iwl3945” modules. In YOUR
case, you’ll need to find out the module names being used by your
wireless device.
modprobe -r iwl3945
modprobe -r ipw3945
modprobe -r iwlagn
5. Save the script and exit the text editor.
[ESC] :wq [ENTER]
6. Navigate to the rc0.d directory.
chmod 755 killwlan
cd /etc/rc0.d
7. Create a link to your killwlan script.
ln -sT /etc/init.d/killwlan S16killwlan
8. Navigate to the rc6.d directory.
cd /etc/rc6.d
9. Create a link to your killwlan script.
ln -sT /etc/init.d/killwlan S16killwlan
10. Now try to shutdown or restart.
init 6
This worked for me. If it works for you, great! If not, sorry for having wasted your time. Good luck!
另外ubuntu8.10的时候就有过这样的问题了，那时候看见过如下的情况：
sudo gedit /etc/init.d/alsa-utils
Search for “stop)” and add immediately below:
ifconfig eth0 down
ifconfig wlan0 down
埃。。当时这个解决方案还很奏效。为什么总是有这样的问题呢。。
