Plugins page error.

Every thing was working fine on my site.

Just few days ago I found a problem searching and installing a plugin. I got following error:

An unexpected error occurred. Something may be wrong with ww.wp.xz.cn or this server’s configuration. If you continue to have problems, please try the support forums.

I googled hours, i found many of same problem thread already active under http://ww.wp.xz.cn/support/forum/how-to-and-troubleshooting.

One of the thread suggested me to add these ips into etc/hosts/ file of the root hosting account
72.233.56.139 ww.wp.xz.cn
72.233.56.138 downloads.wp.xz.cn
72.233.56.139 planet.ww.wp.xz.cn
74.125.47.147 blogsearch.google.com
72.233.56.139 api.ww.wp.xz.cn
72.233.56.142 codex.ww.wp.xz.cn

But in my root directory there is no *hosts* file. Any one please help.