Trying to use the SharePoint List web service (List.asmx) AddAttachment method (http://msdn.microsoft.com/en-us/library/lists.lists.addattachment%28office.12%29.aspx) to add an attachment to a document library item? And seeing a cryptic 'Value does not fall within the expected range' exception? Well, APPARENTLY - this method doesn't work on document libraries (or form libraries): http://social.msdn.microsoft.com/Forums/en-US/sharepointdevelopment/thread/68db70bc-94b1-4dfb-b33e-e42341807583.

Um...wuh?! Yea. I got around it by using the Copy web service's (Copy.asmx) CopyIntoItems method (http://stackoverflow.com/questions/987581/how-do-you-use-the-copyintoitems-method-of-the-sharepoint-copy-web-service). Fortunately I'm creating a new attachment list item, rather than adding an attachment to an existing list item - not sure how to achieve that remotely.

'Scuse me while I go practice my speech to clients on why they should upgrade to SharePoint 2010 and its lovely Client Object Model.