I have pentium 2.4 with xp sp2 512 ram on jetspeed 520i router running on lan with ISDN.My provider has 75kb/s max download and 25 kb/s max upload.Every five minutes my line drops to 0 kb/s or when I open different programs or browse new links on net.The speed gradually goes back to normal speed then again five min. later samething.....why?