Incremental FTP can't open Base File. Error 72 (not supported)

Comodo won’t do incremental backup over FTP with macros enabled. It is a server backup 105 gigs. Transfer went fine, connection is fine. Here is the log.

25.11.2013 22:27:18 Creating New Backup…
25.11.2013 22:27:18 Deduplication is disabled because selected destination doesn’t allow random reads
25.11.2013 22:27:19 Checking if file can be used as backup base.
25.11.2013 22:27:28 Using as base
25.11.2013 22:27:28 Opening backup file
25.11.2013 22:27:29 Unable to open backup base!
25.11.2013 22:27:29 Error Occurred
25.11.2013 22:27:29 Backup failed with code 72 (Not supported).

Any ideas?

What is the name of the backup? You say that it has macros enabled, but “” doesn’t have any macro in it.
A backup with macro should look for example like this:|DATE|_|TIME|.cbu