I started getting this message about a month ago after using TiBu for years. I use SlimRom on a Note 2. It does work to backup and restore to the internal card.
I don't have a problem accessing the external sdcard (sdcard1) from any other app. Rom Toolbox Pro and Helium do not have a problem creating or restoring backups to it. Titanium Backup will usually backup a few apps, as many as 5 or more to as little as none, before it bombs out and displays the insufficient storage message. It is not a problem with storage since I have over 20gb free. My permissions.xml file already has the sdcard permissions set correctly. I have tried updating superuser and forcing system busybox to no avail.
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