Is that the whole message?
Do you see: "cannot find file specified". also perhaps?
OK, as im researching here I am finding some very useful information to help solve your problem.
So far I have found some one else having the same problem but they haven't received an anywhere either.
Also I have found this link stating: "However customers were not able to burn the image or access the partition to make a real backup, therefore a hard drive failure still had the same negative impact."
Furthermore: Dell then re-launched this feature as a service and added a real backup functionality including remote storage. Renamed as “Dell DataSafe Online” the feature was offered as a preinstalled software and web service for selected systems (XPS and Vostro) offering from 3 GB (for Vostro) up to 10 GB (for XPS) online storage at no additional cost for a 12 months period.
I think this imply kind of a potential solution to your problem, or in other words the software is not capable of backing up certain things.
but there is more information there to help you accomplish your needs.
Dell datasafe is unable to handle certain files, in my previous post there is a solution "Dell datasafe Online" is their new service and offers a True backup solution, I recomend you have a look at it and see it you think its right for you.
From a curious point of view are you able to see what file type did not compute with dell and I do recommend you google online backup to find relevent information on potentialy usefull.... information.
This is all I can come up with as I do not work for dell, maybe some one else here will come through and bring a complete solution, if one exists.