hdiutil fails to unmount with error 49153

I'm just getting started with InstaDMG (late to the party I know) and I'm running up against the problem in the subject line. Info: Creating a Tiger train of 10.4.11. External Drive hosting 10.4.11 with a second partition for image creation, attached to a MacMini for post flight ASR restoring. I've relocated my tmp folder to the Imaging partition as the external drive 10.4.11 partition is too small. So far just testing a 10.4.0 install dmg with all Apple updates and Office 2008 pkgs. Everything installs and then this: [code]09:49:12 ######Creating the deployment DMG and scanning for ASR###### Rename the deployment volume: InstaDMG Create a read-only image hdiutil: couldn't unmount "disk3" - error 49153 Scanning image for ASR: ./OutputFiles/08-09-22.dmg ASR image scan complete 09:49:18 ######Cleaning up###### Ejecting images rmdir: true: No such file or directory Removing scratch DMG 09:49:19 ######InstaDMG Complete######[/code] The logs are no more help than this output here. Is it the relocation of the tmp folder? Any ideas?