why I have to start up ubuntu two times?

[baby2843]

this is a question:
when I start ubuntu8.1 ,it often appears that "root.disk doesn't exsited. Dropping to a shell",
but
when I restart it again, I can log in successfully!
Help me.
I am a freshman. Thank you.

[想入非非]

看你的情况大概知道你用的是wubi安装的。。。。不过问题也不好说，不能发现root.disk？