If a big change in game performance happens (check offline too) then something else is probably using up CPU time. You might have some spyware/malware prgrams running and not be aware of it.
Look in the Task Manager, and watch the CPU percentage used. If it is bouncning around 0-2 or 3 percent, then it is running normally.
While in the task manger look for a process named 'rundll32.exe' or run32dll.exe'. I cannot recall which is the correct spelling. If it shows up in the task manager, then you definately have some malware programs running in background.
They will not show up in the process list as they are DLL's. Only EXE's show up in the task manager.
