Acronis Nonstop Backup doesn`t find the USB storage media

I had to format the USB storage unit I was using as storage for Nonstop Backup (I've got a virus). Now Acronis allways shows the message "Partition with the Nonstop Backup cannot be found. Please reselect the partitionor choose another one to store nonstop backups to". But it doesn't allow me to reselect the partition, and I haven't any other storage media to use for nonstop backup.
What can I do to solve the problem?
Thanks!