Hi Karen,
The normal issue that causes this is if you have been running the importer as a different user to the user that is running tomcat, or another user has been changing files (maybe running the filter-media cron job as root etc). Check that all of the directories under [dspace]/assetstore/ are owned by the correct user.
DSpace randomly selects a set of directories to put a new file in, and if one of these happens to not be owned by the same user you are running the importer as, then it won’t be able to write the file, and will stop. So check they are all owned by the correct user or that you have the correct permissions to write to them.
Because Dspace randomly chooses the directories to write the file to, the importer will stop and different places randomly.
Hope this helps,
Stuart Lewis
Digital Services Programmer
Te Tumu Herenga The University of Auckland Library
Auckland Mail Centre, Private Bag 92019, Auckland 1142, New Zealand
Ph: 64 9 373-7599 x81928