Macro takes forever after upgrading from excel 20007 to 2010

I just upgraded from Office 2007 to 2010 and it looks like the macro that I was using for years takes now forever.
When I debugged it, it seems that the time spent on this line consumes a lot of run time:

Selection.Insert Shift:=xlDown, CopyOrigin:=xlFormatFromLeftOrAbove

Here is the subroutine that includes the line:

Sub Insert_Line(sheet_name)
'
    Sheets(sheet_name).Select
    Rows("7:7").Select
    Selection.Insert Shift:=xlDown, CopyOrigin:=xlFormatFromLeftOrAbove
    Range("A8:Z8").Select
    Selection.Copy
    Range("A7").Select
    ActiveSheet.Paste
End Sub

Any idea why is that?