Excel crashing when Pasting Formulas as Values

Hi all,

Would be extremely grateful for some assistance on an issue that I'm currently having.

I recently received an .xls book which I then saved as .xlsx (I'm using 2010). There are just under 8,000 rows and 20 columns. File Size 1MB.

The only formulas in the sheet are the ones in a column which I inserted and copied down for all 8,000 rows. Nothing too complicated: no arrays or anything. The sheet calculates fine.

I am simply trying to copy and paste these formulas as values (into the same cells), though at every attempt Excel crashes. I tried on smaller sets of the column and just got it to work for a few hundred rows, though it struggles with any more than that.

I opened a different workbook of mine, and tried the same operation on twice as many cells containing complicated, lengthy array formulas and the action completed instantly.

There is no Conditional Formatting in the book, no code, no 'last cell' issue, no Named Ranges, no external links.

I have even copied the data to a new workbook, then copied the text of just one of the formulas over into this book, added an equals sign, copied down and recalculated, then tried to paste as values again. Still crashes.

I have absolutely no idea why this is happening. Perhaps my formula:

=IF(AND(N3>1,ROWS($1:1)<>MATCH(M3,$M$3:$M$7979,0)),"Exact Duplicate","")

is far more resource-hungry than I thought, though if that were the case, wouldn't the issue be during calculation (which, as I said, is fine) and not during a paste attempt? No, it can't be this.

I thought I'd ask without a workbook to begin with in case anyone recognises what might be the issue, though I'd be happy to attach it upon request.

Thanks a lot

Interesting. Since writing this, I tried once more and let it run for longer than previously and, after just under three minutes (!), it completed.

Would still like to know if this is normal (can't believe it is) or what may be causing it.

Regards