Excel Can't Right Click

You can reset the right-click menu.

Hit ALT + F11 to go to the VBEditor.

Then View>Immediate Window.

Copy/paste this line into the window and hit

Application.CommandBars("Cell").Enabled = True

OR copy/paste this sub to a module and run it.

Sub reset()
Application.CommandBars("Cell").Enabled = True
End Sub

The Insert and Format not being available could be because the worksheet or
workbook is protected.....I would vote for worksheet.

Tools>Protection>UnProtect Worksheet.

Source:
http://www.wiredbox.net/Forum/Thread327814_i_cannot_use_the_mouse_right_click_in_excel-_how_to_rectify.aspx