>Did you try it in SSMS?

Yes, it was from SSMS.

>Alternative solution would be - create a new table with nvarchar(max) column and insert data from the original table into it (in batches, not all records at once).

I have added a new field and used an update command to replace the new field values with the old field values. It's been running for 5 minutes. So far, this seems to work. I will let you know if that completes and the amount of time it took.