This might have some helpful pointers: T3 Spammers; mp3 Bit-Rates Versus File Sizes & also Most Popular Songs R' Corrupt

Other than that, it could be a trouble-some modem-router not translating properly. Or you may not have your firewalls configured properly. Or you have an aggressive anti-virus or anti-this or that utility that is damaging files before they have completed. Else, try the LW beta 4.12.0 which has lots of improvements in determining what is & what isn't really corrupt: http://www.limewire.com/english/content/beta.shtml (including many other bug fixes & improvements!)
BTW you can see what improvements have been made here http://www.limewire.com/english/cont..._history.shtml