Plugin: Thitter This

Hi,
I’ve just installed the plugin ‘Twitter This‘, but I can’t get it to work well.
When trying to share a post to Twitter the following error message shows up: ‘Warning: file_get_contents() [function.file-get-contents]: php_network_getaddresses: getaddrinfo failed: Name or service not known in /var/…/…’
I’ve searched for solutions, but nothing has been helping so far.

My webserver (Apache2) is running on a Ubuntu platform. . .

Anyone who knows what to do. . .??

Thanks,
Eno