There is a issue in SharePoint 2010 with WebDAV with Windows 7. Just making my readers aware, in case other users of WebDAV ever encounter versions discarded or hung (spinning circle) when saving a document. I’ve seen in for Office 2007 with Windows 7 with SharePoint 2010. This can occur without required fields on a content type, and appears rarely and totally at random.
In a bit more detail, anytime a user interacts with a file through WebDAV, a local copy gets cached on the disk in the temp location C:WindowsServiceProfiles…) and a reference to the file gets created in WebClient’s internal memory. “interacting with a file” means opening and working with it in Office. It also includes anytime you simply touch the file through Window Explorer – getting its properties, even highlighting it with a mouse click counts. Copies of documents are continually being cached and eventually cleared away – it’s normal WebDAV behavior. Of course, only one cached copy per document is supposed to be in that directory. So, if a user opens a file, makes a change to it but doesn”t save it for a while, then go back to the WebDAV location and “interact” with the file – simply clicking on it once is good enough. Wait a few more seconds, and the next time you go to save you open document, the error occurs. What’s happening is the WebClient is grabbing another copy of the file when you click on it, and throwing away its original internal reference – the reference that represents your open document.