I know of at least 2 things that cause that for me: 
 
if they aren't set up for your client, that can happen.  
 
also, if i leave peerguardian up, the level 1 block list is a problem for connecting to a few servers. (a mostly useless list, but i like pg for its simple functionality without making firewall rules.) 
		
	
		
		
		
		
		
		
		
		
		
	
		
		
	
	
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