First of all, using LimeWire isn't illegal and the ISP has no right to disconnect you for using LimeWire if it this isn't a direct violation of his terms of use.

So if you aren't exceeding your bandwidth limit, and your ISP didn't tell you which files exactly he doesn't want you to share, ignore it.

If the ISP told you which files violated any other parties copyrights, - stop sharing those specific files.