Excel version compatibility help

Greetings all,

I have a simple worksheet that uses hlookups to lookup some values from a different file. There is really nothing more complex than that in the worksheet. When I put in the formula and hit enter, I get a number value in return. However, when one of my coworkers opens up the the same file all of the cells are full of #NUM errors. I currently run Excel 2013 and he has 2007, which is the only thing I can think of that is causing this. My other co-workers who use 2013 can open the file and read the number values just fine. It seems that the 2007 users receive the #NUM error. All users are able to open the file that we are referencing in the hlookups just fine.

Can anyone help us figure out why this is happening? Sorry, I can't post the file due to proprietary information issues.

Thank you

=(hlookup($b$1,'file name removed'!$i$3:$ce$65,63))*0.55

There are no problems with the 2013 folks. I've tried having the 2007 people save the file and then open it back up. Still see the #NUM errors on 2007 and number values for the 2013 users.