azureus and telefonica adsl

Hi

i am downloading with azureus quite a while. for two days now as i start azureus all works fine for about 20 minutes. then internet connection goes slower and slower and then drops. As i try a final test to open an internet poage i get to see a DNS error. As i restart the computer all is fine again. What the heck happens there?

gracias por su ayuda

Alex