Can you generate debug output for a sync attempt from the Advanced pane of the Zotero preferences, submit it to the server, and post the Debug ID here?

Thanks.

I got the same error, I had synced from a different computer (linux) all attachments to a new webdav server and tried now to change the webdav server on this (windows) computer, and the error occured. It might be somehow related to files which have an entry for an attachment in the library, but where the file is not present in the local library.

Schwitters

Arvind: This is now fixed in the latest dev builds. It occurs on Windows (due to a Windows limitation) when a file has a very long filename, which generally is only the case for extraneous files with gibberish for filenames saved along with HTML snapshots. Zotero will now shorten such filenames automatically.

The fix will be included in 2.0b7.2, which should be available in a day or two.