have a look in control panel/ administrative tools/event viewer for errors saying that time could not be syncronized.
windows time updates itself every so often,it could be this trying to connect that is dropping your net connection.
check control panel/administrative tools/services and scroll down to windows time,double click and set to manual start up from the list of choices in the drop down list.
restart windows to take effect.
you will now have to update the clock yourself every so often,just double click the windows clock,click internet time and then update.do this about once a week or so.
time.nist.gov is a better time server than time.windows.com