Wireless is less reliable that ethernet cable. Question is, are these files you are downloading Gnutella network files or Torrent files? Torrent files tend to use a high number of connections which can flood some systems. For torrents I'd recommend using Vuse (Azureus) instead.

Other things to try: LW Preferences: Advanced -> SuperReallyAdvanced -> Performance. Disable Ultrapeer capabilities, disable DHT. You could also possibly disable Out of Band searching, however I'd leave that as a last choice. Try these & see if there's any improvement.

If too many incomplete files this can sometimes flood connections also.