Probably is a Java issue. Limewire will not run if your Java is not the correct one for your operating system or if it somehow got corrupted. My computer for years could not DeFrag either and I spoke to a number of Dell Tech people who had no clue why not. I've wiped clean my hard drive and put all the crap back but that didn't even fix it. I'm running an old version of LimeWire and it is simple and very fast, version 4.8.1. If you can find a copy worth downloading it.