Well if you did try deleting your preferences also, then perhaps I was wrong originally. Perhaps the issue is your ISP provider after all. Strange you can upload but not downld. A sudden change where you're not receiving search results sounds to me like what happens to Insight users (another isp.)

OSX preferences are found here: /Users/your_username/Library/Preferences/LimeWire but this file should only be deleted whilst LW is closed.

Another option, set up a new account & install LW there. See if there's any change.

Another option, try Jum's build which is a beta of the betas. It probably won't make any difference but at this point, it's probably worth a try (try the nightly build): http://www.mager.org/LimeWire/ No installation necesary, just mount the dmg & drag & drop the program to your LW program location.