If content was placed into either the Alt1 or Alt2 panel and then a new skin is set on the site that doesn't have Alt1 or Alt2 and the ContentManager.aspx page is used to move that content to a different panel, the user gets the friendly error message and this is logged:
2011-10-04 13:31:04,006 ERROR 0.0.0.0- en-US - /Admin/ContentManager.aspx?mid=999 - mojoPortal.Web.mojoBasePage - 0.0.0.0-en-US - /Admin/ContentManager.aspx?mid=999
System.ArgumentOutOfRangeException: 'ddPaneNames' has a SelectedValue which is invalid because it does not exist in the list of items.
Not really a big issue but an issue nonetheless. I verified this issue on the demo site.
Thanks,
Joe D.