There can be two different causes: the volume you choose is encrypted by TrueCrypt, or there is a malfunction of Acronis low-level drivers due to incorrect registry value
This article applies to:
Acronis True Image Home 2011
You have Acronis True Image Home 2011;
You attempt to configure Acronis Nonstop Backup;
For Acronis Nonstop Backup destination you attempt to select an NTFS partition;
The following error message prevents you from selecting the partition:
Cannot back up to non-NTFS partition
There can be two possible causes:
You are trying to set Nonstop Backup destination to an item encrypted by TrueCrypt.
TrueCrypt is an open-source disk encryption software that allows you to encrypt the entire partition or disk or to create an encrypted file container and mount it as a virtual disk. See: http://www.truecrypt.org/
There is a malfunction of Acronis low-level drivers due to incorrect registry value.
(!) The second cause is specific to Windows 64-bit.