Microsoft Office Excel cannot shift nonblank cells off the worksheet

Hi,
I’m using Microsoft Excel and am trying to edit a large spreadsheet I created a few years ago to track household expenses.
To make my expenses easier to analyze I spent a lot of time formatting the cells and color-coding different sections. My spreadsheet has been working well but when I wish to add a few more rows and columns to track new categories, Excel will not let me.
To insert additional columns I simply select my chosen columns and press the “Columns” option from the Insert menu. When I complete this procedure I receive the error ‘To prevent possible loss of data, Microsoft Office Excel cannot shift non blank cells off the worksheet’.
I do not encounter this same problem when trying to insert rows into my spreadsheet.
Over the years I have inserted many rows and columns into Excel spreadsheets without any problems.
Why am I receiving this error message all of a sudden?
Can someone help me?
