Excel consuming absurd amount of memmory

Question

I have a excel file consuming a huge amount of memmory, something ~500mb.

The file contains only one sheet, no images or scripts and its size is only 719kb.

I have checked all suggested solutions found in some forums, but none worked (http://blogs.technet.com/b/the_microsoft_excel_support_team_blog/archive/2012/12/18/top-10-list-of-performance-issues-in-excel-workbooks.aspx)

The only thing that works is a manual procedure that looks like "black magic":

1. Copy the contents from all cells
2. Create a new sheet
3. "Paste special" the values, comments, values, formulas, validation and formats. Delete the old sheet
4. If you just Ctrl+V into the new sheet it will not work

The lady that uses this excel file in a daily basis does not know what triggers the problem. The only thing she knows is that everything is OK and 5 minutes later the slowness starts. All efforts to extract from her what exactly she has doing at the time to trigger the problem have been in vain

I have attached an example below. Any Help?

https://dl.dropboxusercontent.com/u/2292171/example2014%20%281%29.xlsx