First, I have to tell you, I really admire your work and I am very appreciative of the great product.
I think versioning is completely FUBARing sharing.
A user uploads a file into a shared folder and of the three users with whom the folder is shared, not one can see the file. As admin, I log into that first user's account and delete the file and upload it again. Now only one of the three users can see it.
All of these users have been deleted and recreated. All of the files and folders have been deleted and recreated prior to deleting and recreating the users. A blank slate, as it were, and these issues persist.
After disabling versioning and uploading the file again, it works. Coincidence? Maybe. Tell you next week. BTW, the file in question was a .CSV.
For the record, I am using PHP 5.3.2, on Ubuntu