We're posting the exact same problem on a thread just below here. Was almost convinced it was a hardware problem until I read all the post here. The only thing that has 'worked' is limiting my downloads to one at a time, but even then that only works for an extra couple of minutes.
I'm running 4.1.1 and I've had this problem since i upgraded from 3.8.
Oh look, I've had LW running for all of 6 minutes while i typed this and my connection went on me.......
Sorry but how can it be a hardware problem if (as it seems) everyone's getting this problem with the latest round of Limewire?