Ubuntu8.04关机不正常

[genius0412]

最近一次升级之后，发现系统关机不正常，关机时显示的进度条无法走完，有错误信息一闪而过，之后直接关机，查看系统日志发现如下内容：
Feb 16 03:36:17 genius0412-laptop init: tty4 main process (4680) killed by TERM signal
Feb 16 03:36:17 genius0412-laptop init: tty5 main process (4681) killed by TERM signal
Feb 16 03:36:17 genius0412-laptop init: tty2 main process (4683) killed by TERM signal
Feb 16 03:36:17 genius0412-laptop init: tty3 main process (4685) killed by TERM signal
Feb 16 03:36:17 genius0412-laptop init: tty6 main process (4687) killed by TERM signal
Feb 16 03:36:17 genius0412-laptop init: tty1 main process (5612) killed by TERM signal
Feb 16 03:36:21 genius0412-laptop gdm[5430]: GLib-CRITICAL: g_hash_table_lookup_extended: assertion `hash_table != NULL' failed
Feb 16 03:36:21 genius0412-laptop gdm[5430]: WARNING: Request for invalid configuration key xdmcp/Enable=false
Feb 16 03:36:49 genius0412-laptop avahi-daemon[5131]: Got SIGTERM, quitting.
Feb 16 03:36:51 genius0412-laptop exiting on signal 15

这是什么原因？应该怎样解决呢？
新手