I dont know if this helps but my laptop did exactly the same thing a few weeks ago.It was my Firewall doing the damage.I was running PC tools firewall Plus and my laptop was sluggish and pages taking ages to load along with my documents etc..I uninstalled it, downloaded Comodo security suite and now my laptop is really fast again.
Just disable your firewall and try a new one, ie, Comodo, Outpost or Zone Alarm.
It may be the answer to your problems.
Cheers!