git clone 别人的github项目会提示Host key verification failed

Question

[e-mail]:Unknwon/qiniudrive.git失败！（怎么回事？）
RSAkeyfingerprintisxx:xx:xx:xx:xx:xx:xx:xx:xx:xx
Areyousureyouwanttocontinueconnecting(yes/no)?
Hostkeyverificationfailed.
fatal:Couldnotreadfromremoterepository.
Pleasemakesureyouhavethecorrectaccessrights
andtherepositoryexists.
clone自己的项目不会出现这样的提示。这是怎么回事？
gitclonegit://github.com/Unknwon/qiniudrive.git成功！
为什么[e-mail]:Unknwon/qiniudrive.git失败了？？？