A semi-large file + a shitty computer + using a server = multiple crashes.
It got better when I pasted it into my computer and worked from there. I don't think there was that much data (very long columns, but not many of them), just lots of graphs. It got even better when I deleted all the useless stuff people had put in it.
In another job I had to work with files that had thousands upon thousands of rows and plenty of columns. Just opening them was hell, let alone refresh a pivot table.