hdiutil couldn’t unmount my disk

I've been building images fine since october last year and just this last week, my image creation failed. Here's what the log says 10:46:24 ######Creating the deployment DMG and scanning for ASR###### Rename the deployment volume: InstaDMG Create a read-only image hdiutil: couldn't unmount "disk4" - error 49153 hdiutil: convert failed - File exists Scanning image for ASR: ./OutputFiles/09-03-12.dmg ASR image scan complete 10:46:36 ######Cleaning up###### Ejecting images Removing scratch DMG 10:46:36 ######InstaDMG Complete###### I thought it may have had something to do with a recent apple update or custom package, so I rolled back to the last working image config. That failed as well. I am looking in the /tmp folder right now and I see three versions of the instaDMGMount.* folders. They all are all full images that seem to have been unlinked to the original disk image and stuck! I'm not sure I'm using the proper terms to describe the issues, hopefully you can follow what I'm saying. They look like alias folders. I tried to eject them, but that's not an option. Show original takes me to the computer view in finder. Right now I'm rm -R them, but it's taking a while. I know my machine has had some issues with mounted disk images and not ejecting them properly. Should I rebuild my image machine? If I delete these folders, do you think I'll be able to create a new image? Is there something else that the logs point to? Thanks Rusty