it could be that you had too many connections open. When I first started playing around with gnucleus I tried (keep at least 8 open and a max of 10), I thought that the more host connections the better. My system slowed to a crawl after a couple of hours then crashed. I have since settled at keep 4 open and max 5, with this configuration I have been up for 12 days with no slow down or crash.

F.Y.I : my sytem looks like this - p-III 866- 512 meg pc133 ram
win xp- 1 mb/s cable line.

I set my upload bandwidth to 200kB/s max

Try this out, I hope it helps