Really Delete Blank Empty Columns

I have data in Columns A:CN. I copied a formula in CN to the last column of the worksheet (ok, not the smartest move). I then deleted the formula from CO to XFD, the last column. When I tried to insert a new column in my data range A:CN, I received a message that it would not move non blank cells off the worksheet. Sure enough Ctrl+End brought me to the last column XFD. I deleted the columns CO to XFD by selecting the entire columns and right clicking on delete and by using the delete sheet button. But Ctrl+End still brings me to XFD and I can't insert a new column. How can really delete these blank empty columns?

You sure can. You'll need to delete columns CO:XFD, save, close the workbook, and reopen it.