Yo m8,
in short there is no adware or trojans in genuine limewire, it does not cost 20 bucks its 18.88 dollers if my memory correct. Basic is free give that a try. A lot of scam sites look very similar to the correct one.
http://www.limewire.com/english/content/home.shtml
I cant recall any problems wiv ur adware protection someone may correct me here but they are both on my favorable list. Your av iv had nothing to do with but have heard good things about it so would be surprised if that was the problem.
Download the basic from this link and report back.