I have to deal with CSV files output by some commercial software which
is not properly written. It gives long lists in which some of the rows
have more columns than others. These lists can be thousands of lines
long, so I wrote this macro, which moves the offending rows back to
where they should be.

First, I manually open up enough columns so that the rows can be moved
to the left. Then I establish which is the rightmost column containing
data, and I go to Row 1 and run the macro.

It works fine, except that it crashes at row 65535, instead of simply
ending because it has dealt with every cell in the column. I have
highlighted where it crashes, and would appreciate anyone who knows why
this happens.

Sub Line_up_cols()
'
' Keyboard Shortcut: Ctrl+Shift+L
'
Dim myRange As Range
Dim Cell As Range
For Each Cell In ActiveSheet.Columns()
Selection.End(xlDown).Select
Selection.End(xlToLeft).Select
Set myRange = ActiveCell
Range(Selection, Selection.End(xlToRight)).Select
Selection.Cut
myRange.Offset(0, -1).Select <<<<---- Crashes here
ActiveSheet.Paste
ActiveCell.Offset(0, 1).Select
Selection.End(xlToRight).Select
ActiveCell.Offset(0, 1).Select
Next
End Sub