MS Excel, Macro appending extra characters

Using a macro, I'm joining 2 separate sets of columns with a colon using a simple function, like =A2&":"&B2

This works fine until it gets to the final row, where the macro is adding two additional cells each with just : in them. It looks like the macro auto-selected past the fields that contained data and joined the empty cell contents with the :.

I've reviewed the macro several times and don't see what might be causing it. Can someone spot check this for me?

Sub NetworkStatisticsFilter()
'
' NetworkStatisticsFilter Macro
' Format and Filter Data from Get-NetStatTCP to simplify port discovery
'
'
'Suppress alerts
'
    Application.DisplayAlerts = False
'
'Delete empty header rows that resulted from Get-NetStatTCP export
'
    Rows("1:1").Select
    Selection.Delete Shift:=xlUp
    Rows("2:2").Select
    Selection.Delete Shift:=xlUp
'
'Text-to-Columns, space-delimited
'
    Columns("A:A").Select
    Selection.TextToColumns Destination:=Range("A1"), DataType:=xlDelimited, _
    TextQualifier:=xlDoubleQuote, ConsecutiveDelimiter:=True, Tab:=True, _
    Semicolon:=False, Comma:=False, Space:=True, Other:=False, FieldInfo _
    :=Array(Array(1, 1), Array(2, 1), Array(3, 1), Array(4, 1), Array(5, 1)), _
    TrailingMinusNumbers:=True
'
'Join LocalAddress & LocalPort with a ":" then copy results and replace both columns w/a paste-value
'
    Columns("C:C").Select
    Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
    Columns("C:C").Select
    Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
    Range("D1").Select
    ActiveCell.FormulaR1C1 = "SRC"
    Range("C2").Select
    ActiveCell.FormulaR1C1 = "=RC[-2]&"":""&RC[-1]"
    Range("C2").Select
    Selection.AutoFill Destination:=Range("C2:C77")
    Range("C2:C77").Select
    Selection.Copy
    Range("D2").Select
    Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
    :=False, Transpose:=False
    Columns("A:C").Select
    Range("C1").Activate
    Application.CutCopyMode = False
    Selection.Delete Shift:=xlToLeft
'
'Join RemoteAddress & RemotePort with a ":" then copy results and replace both columns w/a paste-value
'
    Columns("D:D").Select
    Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
    Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
    Range("E1").Select
    ActiveCell.FormulaR1C1 = "DST"
    Range("D2").Select
    ActiveCell.FormulaR1C1 = "=RC[-2]&"":""&RC[-1]"
    Range("D2").Select
    Selection.AutoFill Destination:=Range("D2:D77")
    Range("D2:D77").Select
    Selection.Copy
    Range("E2").Select
    Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
    :=False, Transpose:=False
    Columns("B:D").Select
    Range("D1").Activate
    Application.CutCopyMode = False
    Selection.Delete Shift:=xlToLeft
'
'Auto-fit columns
'
    Columns("A:D").Select
    Columns("A:D").EntireColumn.AutoFit
'
'Auto-filter loopback address/port combinations and delete resulting rows
'
    Columns("A:A").Select
    Selection.AutoFilter
    ActiveSheet.Range("$A$1:$A$79").AutoFilter Field:=1, Criteria1:="=127.0.0.1*", Operator:=xlFilterValues
    ActiveSheet.UsedRange.Offset(1, 0).Resize(ActiveSheet.UsedRange.Rows.Count - 1).Rows.Delete
    ActiveSheet.ShowAllData
'
'Remove duplicate values in DST column
'
    Selection.AutoFilter
    ActiveSheet.Range("$A$1:$C$67").RemoveDuplicates Columns:=2, Header:=xlYes
    ActiveWindow.SmallScroll Down:=-9
'
'Allow Alerts
'
    Application.DisplayAlerts = True
End Sub