I've used some code which I usedin antoher file to delete empty rows.
Maybe of use for other people:

Sub hiderows3()
Dim NullRange As Range
Set NullRange = Nothing
For i = 1 To ActiveSheet.UsedRange.Rows.Count
If Range("J" & i).Value = "" Then
If NullRange Is Nothing Then
Set NullRange = (Cells(i, 1))
Else
Set NullRange = Union(NullRange, Cells(i, 1))
End If
End If
Next

If Not (NullRange Is Nothing) Then
NullRange.EntireRow.Hidden = True 'hide the rows which satisfy the
condition.
End If
End Sub