Editing Problem in Grouped Worksheets

We have a workbook with four Worksheets.  The worksheets are protected but right now protection is turned off.  We have two the four grouped together and when you try to edit information in a cell it will not accept the change.  If you totally replace it with new text it will accept.  When you add additional text (it is a description cell) and hit enter it just reverts to what was there before.  Am I missing something obvious?