Wierd Internet Problem

for the past few days iv been facing this wierd problem my isp is sify:

now the problem is that after i shut down pc for a few hours and then turn it on again and try to connect to the net the dialler logs in but no page is displayed in any browser

now im usually in vista now to rectify this problem for some reason i need to go into xp disable my lan for some time and then enable the lan again now when i login and browse everything seems fine