VBA Sort Sorting VLookup Values Totally Randomly

[ransomedbyfire]

I have a sheet with VLookups that pull rankings of other values in Excel 2007. The sheet I am trying to sort has return values (percentages) in column N and rankings in column M. I am trying to sort the values in columns A-Y by the rank values in column M (from smallest to largest); but when I run the sort, the order of the values looks completely random.

Here is my code:

'Finds the last row
lastrow = Range("a:a").Find(what:="", after:=[a13]).Row

'Sorts sheet contents by rank
    ActiveWorkbook.Worksheets(4).sort.SortFields.Clear
    ActiveWorkbook.Worksheets(4).sort.SortFields.Add Key:=Sheet4.Range("m13:m" & lastrow) _
        , SortOn:=xlSortOnValues, Order:=xlAscending, DataOption:=xlSortNormal
    With ActiveWorkbook.Worksheets(4).sort
        .SetRange Range("A13:Y" & lastrow)
        .Header = xlNo
        .MatchCase = False
        .Orientation = xlTopToBottom
        .SortMethod = xlPinYin
        .Apply
    End With

Any help would be greatly appreciated! I'm totally stumped here!