Basic file, no pictures, no formulas, huge memory and cpu usage

I have been having a problem with the attached file where just clicking around the file in different cells and doing nothing else uses max 50% cpu usage (2 cores i assume). It also uses 300+mb of memory. I have bigger more complicated files that use more sheets and more columns that use 10 times less memory and have hardly any cpu usage at all. I have no idea what is causing it as there are NO formulas, NO conditional formatting, NO macros and NO pictures in this file! It doesnt even use a large number of cells.

I am using office 2010 pro 32bit and windows 7.

Any ideas? I have attached the file in question.