User-Defined Function Auto-Completes but gives #NAME? Errors

This problem happens on my laptop but not for my co-worker, so it seems to be related to my laptop, settings, etc.

I wrote a Visual Basic function in an Excel .xlsm file using Excel 2010 a couple of days ago, and it worked fine. Today I opened the file, and the following errors are occurring:

• If I copy a tab in the spreadsheet, the tabs using the functions display #NAME? in the cells where it is used. I don't get this problem if I instead insert a new tab.
• If I copy a line on the tab using the functions or drag a cell using the function to the next line, the cells where the functions are used display #NAME?
• If I enter the name of the function in the formula field for an empty cell, auto-complete recognizes the name, but if I fully type in the function name with a parameter, the cell displays #NAME?

If I send the Excel file that is giving me the #NAME? errors to a co-worker, when she opens the file, it displays the #NAME? error, but she acknowledges the 'Enable Content' warning, and the #NAME? errors are removed. She can then simply save the file and email it back to me, and the #NAME? errors are gone. All of this points to something being wrong with my laptop, Excel settings, etc. but I have no idea what to look for with this behavior.

Does anyone have any suggestions?

Thanks in advance

One additional piece of information: Once I receive the file back from my co-worker without the #NAME? errors, any edit that I described in the original post causes the #NAME? errors to occur again.

Thanks