I am having what can only be described as "block selection lag". I can select all manner of objects all day long but every minute or so when I try to select a block, it doesn't seem to matter which one, I have a delay of 2-5 seconds then everything goes back to normal. I can deselect the block and re-select it (or other copies if a multiple) with no lag for a minute or so then without warning the selection lag returns. Repeat for the next 8 hours. There is no connection between drawing size; the issue happens on large and small drawings alike.