Are you living in an apartment complex? Try & find out for sure who the building's ISP is. There might be a firewall associated with your building's internet...can you ask the manager or whoever's in charge of internet access?

You could try changing ports. In LW go tools > options > advanced > firewall config. Change LW's listening port to 64049, or something in the range of 49152 - 65535.

You should think about getting an AV program There are good, free ones available which won't interfere with LW. Check these out.

avast!

AVG free

Avira Antivir