Error ID: 1424968125 Sync Error: ERROR UNDEFINED

After update to new Zotero Version 4.0.10 in Chrome (V 28.0.1500.95 m) and Firefox (V 23.0)already existing Group- and Local-Databases could not be synced with Zotero Server due to suspicious ERROR UNDEFINED message:

[JavaScript Error: "Error undefined C:\Users\mhirsch\Documents\ArchivUnterlagen\Zotero\storage\8TV997H7\FILE.pdf" {file: "chrome://zotero/content/xpcom/storage.js" line: 1064}

Respective file.pdf is not open while syncing.

C:\ is of course a local drive.

15 people within the same group library recognize the same error BUT about DIFFERENT files!

Even reset from server does not help.

Reset sync history does not show any effect.

Deleting and re-enter a respective FILE.PDF Zotero entry causes the same problem.

Thanx for help.
This discussion has been closed.