Maybe Limewire doesn't have a problem with mp3 files. Maybe the RIAA does, and when they detect someone sharing files with that extension they try to flood them off the net? Limewire might be freaking out due to huge amounts of malformed traffic intended to bring it down or degrade its performance. Even if you have just legitimate mp3s, maybe the RIAA still takes a preemptive "shoot first and ask questions later" approach...wouldn't surprise me at least to find them playing dirty in such a way!