suitable backup target partition for selected element not found

“suitable backup target partition for selected element not found”

The is roughly the translation of the error message I get (in german) when trying to initiate my first full backup with CB, by clicking on “system backup” in the top, light-blue panel on the home screen that says “(My Name)'s Computer”.
I have an external harddrive to backup to with 300GB of free space, and an internal storage partition with about 60 GB of free space.
The system partition that i want to backup is 65 GB.
Is CB not recognizing the external harddrive? Cause it’s fully operational in the system (Windows XP, btw). How do I make CB see it?
thanks, Ben

EDIT: I just tried again by just clicking “backup now” in the second-from-top grey panel saying “backup”
I select the system partition and start backup, I get Error code 49


The issue with System Backup button will be fixed in the next release.

Error code 49 means device not ready. Please post the log or a screenshot with this issue.