Do you see a brick wall in front of the blue world icon at the bottom of LW's interface?
Try an experiment, try downloading a magnet link from here
http://www.magnetmix.com/video.shtml & tell us what happens. All you need to do is click on one of the download links & LimeWire should then handle the file.
Edit: I did some searching around. I can't find anything that suggests your ISP is filtering (other than the link below), but that doesn't mean they don't filter or block p2p sharing. Clearwire who you probably know of, do shape bandwidth for p2p sharing.
But Eircom apparently are shaping for Bit Torrents:
http://yro.slashdot.org/comments.pl?...3&cid=14655408 (from discussion here http://yro.slashdot.org/article.pl?sid=06/02/06/2039241)
http://www.irishisptest.com/forum/cl...broadband.html (post 15)
http://www.irishisptest.com/forum/se...?searchid=2437
http://www.irishisptest.com/forum/eircom/