Well, had to start using ACAD Civil3d today and boy was it lagging after I click anything.  I turned on the Task Manager to watch the CPU and when I just hovered the mouse over an item, the CPU was about 10%.  When I clicked on the item, the CPU spiked to 50%!

The solution?  Well, there may be many, but what helped me was simply closing the properties window.  Yeah... really simple thing to do, though I know it is a helpful thing to have open.  But when I had the properties window open, every time I selected an item(s), the computer would lag for a second or two.  When I closed the properties window, the lag disappeared.