Create two files test2.xls and test2.xlsx. Place value "42" in cell A1.
Create file test1.xls. Paste in cell A1 a link to cell A1 in test2.xls and in cell A2 a link to cell A1 in test2.xlsx. Save and close file. Open it again. This works OK.
Save test1.xls as test1.xlsx. Close test1.xlsx, and then open it again. The links get corrupted, e.g.:
*** This bug has been marked as a duplicate of bug 76047 ***