I have seen this error in the past. I have had jobs run for years without any issue then all of sudden it stopped working. Unfortunately I cannot find the Microsoft KB reference about it but, if you are running the DTS package under the SA in your job change it to the NT account that is running your services and ensure that the NT account has access to the folder where the data is stored. For a SHORT TERM fix (and I do not recommend it) you can also change the owner of the job to your own NT account or any other NT account that has access to the folder and has the correct level of Privileges to run the job.

Hope this helps, if not let me know.