hmmm. tried a reboot of your router?

could be to do with dhcp trying to re-assign your ip address every hour?
check for something like 'dhcp lease time' or 'client lease time' in your router setup or similar

or do a Start->Run-> type 'cmd'
and do 'ipconfig /all'

and note the 'lease obtained' and 'lease expires' times. for ideal usage, they should be 1 day apart