Excel will not allow Zero values to be reformatted

I teach an intermediate Excel course and have a student's file that is acting.. funny. I have never seen this issue before and would like some ideas on what could cause it/how to fix it. I have attached the file.

In cell I3:J3 she has entered the value 0. The cell will not allow the number of decimal places nor the number formatting to be changed. The Automatically Insert Decimal point option is not enabled; the worksheet is set to calculate automatically. Moreover, the same thing occurs when a 0 is entered anywhere on the sheet.

I thought maybe it was being caused by a trailing "ghost" character, and when I nested the 0 value inside the TRIM function, the extra two decimal places went away but I was still unable to change the number format. Any ideas?!!?

Try this:

1. Select I3:J3 -> Clear -> Formats

2. Merge & Center

Thank you everyone! Conditional formatting.. of course! :P