After getting the new patch, I deleted all my old FTM trees from my hard drive, then unlinked and re-downloaded all my trees. It was working great today, syncing several times today, very fast, with different trees, updates to the FTM and/or online Ancestry trees was working very well.
Went to do one last sync this evening and got the dreaded "An error occurred while synchronizing this tree. You can try again later..." Tried compacting, etc. Opening and closing FTM. It hung a couple times and I had to kill it via Task Manager. And, I was able to successfully sync another small tree even though my large one is now failing.
I have reported all details to my contact at Customer Support. I have been saving screen shots in a Word document as I go just in case... and to make it easier for them to diagnose if something did go wrong.