Problems making a backup imagine

[ajcowell]

I'm backing up my powerbook to a firewire drive. Back works fine. Problem comes when trying to unmount the drive to create an image. The end of the log is shown below:

|11:04:22 AM|Info| Scanned 111794 items occupying 8.64 GB (21149 directories, 87737 files, 2908 symlinks)
|11:04:22 AM|Info| Copied 2978 items totaling 8.57 GB (28 directories, 44 files, 2906 symlinks)
|11:04:22 AM|Info| Cloned 8.57 GB of data in 135 seconds at an effective transfer rate of 64.99 MB/s
|11:04:22 AM|Info| PHASE: Conclude Target Setup
|11:04:22 AM|Info| ...ACTION: Bless System on Target
|11:04:22 AM|Info| ......COMMAND => Blessing OS X System Folder
|11:04:22 AM|Info| Successfully blessed Mac OS X folder on Firewire
|11:04:22 AM|Info| ......COMMAND => Blessing OS 9 System Folder
|11:04:22 AM|Info| Did not bless Mac OS 9 System Folder on Firewire because it does not exist.
|11:04:22 AM|Info| ...ACTION: Create ASR Image
|11:04:22 AM|Info| ......COMMAND => Checking to see if volume Firewire can be unmounted safely
|11:04:25 AM|Info| Could not unmount volume Firewire
|11:04:25 AM|Info| Checking for open files on /dev/disk2s3...
|11:04:26 AM|Info| COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
|11:04:30 AM|Error| Could not unmount Firewire

It seems it's looking to see if there are any open files but can find none. Help!