Macro taking too long to execute

Greetings all

I have been working on a macro this week that will insert a row underneath the header and write the formulas to the proper cells so that we can record production in a reasonably efficient manner. I do not claim to be a macro magician and I am sure there are better ways to accomplish some of the things I am doing, but it seem as though this particular macro has taken it upon itself to run too slow to be useful at all. The entire macro, comments and all is only 266 lines long (and there are a lot of comments as I wanted someone else to be able to go in a tell what was going on). It seemed to be working fine yesterday and I have been putting the final formulas in today before working on the formatting. When I tested it before lunch, it froze, so after lunch I ran it in debug mode and it isn't hanging on the back end where I have been working today, but at the very beginning. Can someone please take a look at this and see if there is something I am missing that would cause it to hang up?

Sub Production_Register_Line_Add()
'
Dim lrow As Long
Dim Gm_Lb As Double
Dim Gm_Oz As Double
Dim History As Integer
'*********************************************************************************************
        Sheets("Variance Register").Select
'*********************************************************************************************
        Range("7:7").Insert shift:=xlDown
        Range("6:6").Copy Range("A7")                                               'This line is taking in excess of 30 seconds to execute
            'On Error Resume Next
        Rows("6").ClearContents
'*********************************************************************************************
'   Declare Values for Constants
'*********************************************************************************************
        lrow = Worksheets("Variance Register").Range("A" & Rows.Count).End(xlUp).Row
        Gm_Lb = 453.5924
        Gm_Oz = 28.349527
        History = 180   'Number of days history to use when calculating Unit Cost Averages
'*********************************************************************************************
'
'   A - Manufacturing Date (date when batch was actually made)
'   B - Fill Date (Actual Production Date)
'   C - Batch Number (Number stamped on jars to identify manufacture Batch)
'   D - Finish Good Number
'   E - Item Description
'
    Range("E6").Formula = _
        "=IFERROR(INDEX('\\Network\Company\Product Data\Product Data v1.00.xls'" _
        & "!Item_Desc,MATCH($D6,'\\Network\Company\Product Data\[Product Data v1.00.xls]" _
        & "Product Data'!Item_No,0)),"""")"

' This index(match()) is also taking in the neighborhood of 30 seconds to execute  and I have 4 of these lookups 
'more stuff
end sub

Right now, I have data going out to column BP and a little over 3,100 rows

I would appreciate it if anyone could see what I am doing that would cause this thing to hang up like it is.

Thanks

Thanks for your response!

I tried it, but without any success. It still took about 4 minutes to execute the macro. One thing I noticed while watching the screen not do anything, was that the program would alternate between being responsive and not responsive. I wasn't trying to do anything else at the time, just watching. I took out the screenupdating statements and tried again and it still alternated between responsive and non responsive.

When I insert the row

        Range("7:7").Insert shift:=xlDown
' I insert the row 2 rows below my headers so that I copy the formats of the data area and not the formats of the header row.
        Range("6:6").Copy Range("A7")
' The Range("6:6").Copy copies the data residing on row 6 and pastes it to row 7 giving me an empty row 6 at the top of the data.
        Rows("6").ClearContents
' Rather than a cut/paste of row 6 data to row 7, I have always used a copy then clear data.  Call me paranoid, but if it blew up at that time, I wouldn't need to go back and 
' rebuild data, just start over.

Actually, the file Product Data is almost always already open, so it seldom has to actually open it. It isn't making any sense to me either.