Up until today, Excel worked fine and I was able to insert rows and columns, copy rows and columns and Insert Copied Cells, and format cells by selecting, right-clicking, and choosing Format Cells. Today I can't do any of those things. I have searched all over the internet and all I have found is people asking "is it a shared workbook?" or "is the sheet protected?" I'm not an Excel idiot so I assure you the answer to those questions is no. It happens if I open a brand new workbook or an existing one, if I copy and paste special values or just type new values in the cells. What could possibly be causing this?