Excel melts down when I try to refresh data

try this

select all column & rows which doesn't content data & delete them once do this in all sheet, & then save workbook ......then check size

may be this will help

It helped a tiny bit. It took longer for Excel to crash. Unfortunately, it seems that when it starts "Calculating PivotTable report," it hits that memory threshold and it crashes.

I'm going to take the files home and see if it crashes on my computer which is 64-bit and has 64-bit Excel 2013...

good luck .......

Well, I decided to add those local workbooks as external data connections instead of directly referencing their cells. Looks like that fixed the problem. I'm guessing Excel was opening that workbook (about 32MB) each time... that would add up.