OK, so I seem to have resolved this.

This is what I think happened: at some point I managed to include attachments with various entries in my local cache of the group library. But on zotero.org this library was configured for public (read) access, and when a library allows public access then attachments (file storage) are not allowed. So it seems that the next time I tried to do a sync, this then failed.

OK, with the benefit of hindsight, this is indeed what the diagnostic told me: "You no longer have file editing access to the Zotero group '[foo]' and files you've added or edited cannot be synced to the server." Sort of. But I was thrown off by the "no longer" bit (which suggested I did have access to do this at some point previously, but now no longer had it - which was not the case at all, and really quite misleading/confusing). And also, I confess that I didn't grasp the significance of the word "file" (as opposed to, say, "entry") in the message.

I don't think I can be the only one who might fall into this trap, so I would urge the developers to try to arrange a more precise diagnostic for this condition, if at all possible.

I'm not entirely sure how the local attachments got added; but I suspect I was exploring the preferences at some point, and ticked "Automatically take snapshots ..." and "Automatically attach associated PDFs ..." without digesting the potential impact of this on syncing with a group library. In any case, I have now switched these off again, to be sure.

How did I fix this up? First I exported backup copies of the local (cached) versions of each collection in the group library. I the attempted the sync again, let it fail as usual, but this time allowed it to go ahead to discard the local copy of the library and then repopulate it from the zotero.org version (previously I had just cancelled out of the sync instead). This then gave me a clean, synced, copy of the group library. I checked that I could make a change and resync, which now worked correctly again. The catch, of course, was that I had now, in principle, lost an unknown set of changes that had been accumulated in the previously cached (and now discarded) version of the library. I don't know an easy way to automatically check this. I did re-export the now re-synced collections, and attempted to compare with the backed up copy of the previously cached version. The main, obvious, discrepancy was that the re-synced version lacked content in any "files" subdirectory, whereas one of the cached collections did have such content (which is consistent with my diagnosis above of what caused the problem). I did attempt to compare the .rdf files to see if there were more subtle changes; but a simple diff does not seem to work, due to at least some arbitrary (and unimportant) re-ordering of entries. I finally settled for doing some spotchecks, and doing a diff on sorted versions of the .rdf files (which, of course, gives nonsense in an xml sense, but a reasonable "hash" for order insensitive comparison purposes) which found no discrepancies. But, of course, your mileage may vary.

Regards - Barry.

Report id: 1053998817
"You no longer have file editing access to the Zotero group 'Creativity in communication (CraC) Unitec NZ', and files you've added or edited cannot be synced to the server."

I created the Zotero group, and still remain as administrator. So I do not see why I no longer have file editing access. I had cancelled group sync using Zotero several months ago. Today I re-initiated group sync. The other groups I created - with the same settings - function without generating an error.

I have also established a personal file sync using webdav on my imac disk. That seems to have worked without error messages to me, though I note in the report log there may be some unrelated error messages concerning my webdav file sync.

I am reluctant to follow * adm.aishe's advice of Nov 16th 2009. Advice please.

Dan: It may note this when you are creating a group, but I went to open my group up to be more visible, and, silly me, checked Public/ Open Membership.

KAPOW! BAM! CRASH! holy s__, batman! it apparently deleted all attachments.

This is obviously operator error (I did it), but perhaps a message when changing group type might prevent another soul from having his heart stop. (I fortunately have a backup and am attempting to reset (having changed the group back)
Doug