After entering cell's editing mode, it will fail to create formula by function dialog.
This issue was occurred on all major IE browsers from 8~11.

reproduce steps:

1. open a blank file
2. select a blank cell. e.g A1
3. press F2 to enter cell editing
4. click function button on left of formula bar to popup function selection dialog
5. select any function and fill arguments, e.g =ABS(-1)
   • cell is still empty and no focus, however, formula bar has selected formula
6. select other cell to apply editing, e.g select A2
   • such formula is applied to cell, BUT quickly replaced with blank.