Two options: 1) Create a batch script that first kills Firefox and then runs the FFS sync 2) Run FFS as admin and enable "copy locked files". This will use the Windows VSS to get a copy of the files, even when in-use.
It's important to me that I have a backup of my FireFox profile. Using a small app called fBackup I have come up with a list of essential files and folders to backup. I have also found the important plugin data folders and can back those up too. I do this to avoid having a gigantic backup that ...