I just tried this on a sample database and it worked without a problem. Possibly you have some bad data in the Order field. See if simply using FormulaFill «Order» instead of the ZeroBlank version causes a crash as well.
There isn’t any need for the chevrons in this case (since Order has only alphabetic characters), but it shouldn’t hurt anything either. I think Gary might be on the right track, perhaps there is some sort of corruption in the database. I haven’t ever heard of this before. Is this the entire procedure you are running? Is there any other code that might be what is actually causing the problem?
I did make a database with an Order field and try the exact code @panaca specfied, including the chevrons. It worked perfectly, and changed zeroes in the column into empty cells, as desired.