i think my Excel quits before my Macro is done?

I wrote a macro that I use to analyze the outputs of a 2-d hydraulic flow model.  It gets rid of the junk data and moves the data I want to analyze near the "origin" of the webpage.  It worked on a pretty large data set when we had a 3' sized grid, but the excel crashes when I run it on the output of a 1' sized matrix.  It is about 4500 x 4500 cells in size before I run the macro.  The macro looks like:

Sub removeinplace()

‘This sub replaces all of the junk data (-9999) with blank cells but does not affect cells that do not have (-‘9999) in them.

‘This sub calls DeleteBlankColumns and DeleteBlankRows to move the cluster (it is a contiguous

‘cluster) ‘of data closer to the origin where I can work with it.

'   define Myrange

    Set MyRange = ActiveSheet.UsedRange

  With ActiveSheet.UsedRange

    .Replace -9999, "", xlWhole, SearchFormat:=False, ReplaceFormat:=False

  End With

Call DeleteBlankColumns

Call DeleteBlankRows

End Sub

Sub DeleteBlankColumns()

‘This sub deletes blank columns

'Step1:  Declare your variables.

    Dim iCounter As Long

    Dim MaxColumns As Long

'Step 2:  Define the target Range.

    With ActiveSheet

    MaxColumns = ActiveSheet.Range("B1").Value

'Step 3:  Start reverse looping through the range.

    For iCounter = MaxColumns To 1 Step -1

'Step 4: If entire column is empty then delete it.

       If Application.CountA(Columns(iCounter).EntireColumn) = 0 Then

       Columns(iCounter).Delete

       End If

'Step 5: Increment the counter down

    Next iCounter

    End With

End Sub

------------------------------------------------------------------------------------------------------------------------------------------

Sub DeleteBlankRows()

‘This sub deletes blank rows.

'Step1:  Declare your variables.

    Dim iCounter As Long

    Dim MaxRows As Long

'Step 2:  Define the target Range.

    With ActiveSheet

    MaxRows = ActiveSheet.Range("B2").Value

'Step 3:  Start reverse looping through the range.

    For iCounter = MaxRows To 1 Step -1

'Step 4: If entire row is empty then delete it.

       If Application.CountA(Rows(iCounter).EntireRow) = 0 Then

       Rows(iCounter).Delete

       End If

'Step 5: Increment the counter down

    Next iCounter

    End With

End Sub

What am I doing wrong?

(I wasn't able to load sample data because it was too large of a file).