From time to time when I've been out of town working with offline files, I would get an "Incorrect Parameter" error when I tried to synchronize the files (usually when I had returned home and was plugged directly into our network).  This happened to me when out of town recently at the end of a day when I'd created quite a few files (a few hundred) in a customer's folder tree.

I thought it might be related to creating so many new files so I copied the bulk of the new files (fortunately, they were mostly located in a single four-deep folder set) to a temporary folder on my laptop then deleted them from the offline files.  Also, note if you've created folders while offline but have not synchronized them yet, you can still delete the folders while offline.  If they've been synchronized, you can't delete them unless you're online.  [more]

I then connected via Cisco VPN and tried to synchronize and it worked.

Finally, while online, I copied the new folder set to the customer's folders online (which copied them directly to the server) then synchronized to get them back into the offline set.

The alternative was to work on an offline copy then manually synchronize them once I was back in the network and to nuke my offline files to get synchronization to work again.  This is what Microsoft recommends and I've done it numerous time.

This was a preferable solution.