One thing comes to mine, and it depends on how many formulas are effected when you insert the new line.
When you insert the new lin, Excel will relatively ajust all your formulas. If you have a large spreadsheet this can take some time. If the is the cause of your problem Excel will display the word "Calculating" and display a progress bar on the status bar.
You can fix this by placing Excel into Manual calculation Mode. (Click on Tools - Options. Click on the Calculation Tab, and select the Manual option from the calculation area.)
Now you can insert you new line(s), when you have finished press the F9 key on the keyboard to have Excel recalculate you spreadsheet, this will still take 2 minutes, but you will not have to wait2 minutes every time you change something,
Hope this helps
Mike Dale