Error while checking URL: 6, name lookup timed out

Hello

I have sucessfully installed Leech. I have added some RSS feeds. Leech sucessfully has the RSS Feeds importet.

Now I can not add more Feeds. I get the following error:
Error while checking URL: 6, name lookup timed out

I have installed the Zend Optimizer before. I have deinstalled the Zend Optimizer. The Problem is still alive.

Does Anybody know what I can do to made Leech running again?

thx
benjamin