Is it doing this all the time now even after you restart your laptop? I'm sure you have probably done this already (!) but I wouldve tried to free the ram at the time - using freeramxp or similar click here
as there could be something in the background hogging your ram (cntrol+alt+delete to check), or have done a virus scan just to be safe (im paranoid!).
Also, have you downloaded or installed any files/applications recently (internet related or not), which could lead to the cause?