In his Smurf on spreadsheets blog, Simon Murphy highlighted a data linking anomaly that causes reference errors when you open a worksheet that contains the source cell for an external link
As described by Smurf, the problem can be replicated by opening two workbooks and saving them as .xlsm files.
If you put text in a cell on one workbook and link to it from the other and then save and close both workbooks, when you reopen them (source file first),
Latest questions on 
