I seem to be having problems with large Excel files. In particular, one file has (had) about 56,000 lines with maybe 20 columns. Calculations in some of the columns. This file became corrupted and unrepairable. Since it was made of of a bunch of smaller files, I have rebuilt it and eliminated all but three columns, with no calculations.

Still, when I tried to change the font in one of the columns, it took a long time and still did not change the font in whole column. I had to divide the group into smaller sections to do it.