Strange Internet Problem in Vector Linux!

I have been facing a strange problem in Vector Linux...
I can connect and surf net..but sometimes even after i connect(using pppoe-start), m not able to surf!!

ifconfig shows all the three interfaces lo,eth0 and pppoe0 running!

I reboot into windows and the net is working!!!

Then if I try connecting to net in Linux after a day or two...I find net working again!!

I have no idea of whats going on!! HELP!!