>>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.

Is your table partitioned? It may be a good idea to partition it.