this is not enough information. ALWAYS declare what version and configuration of software you are using!!!
Down to your error - maybe service account does not have enough privileges (FULL ADMIN rights) to write to certain locations, but it is hard to tell since you are not telling us if your report needs to be stored on HDD or send to NewsStand or mabe send via email.
Provide more info and maybe we will be able to help you
cheers Lech, When applicable please mark the correct/appropriate replies as "solution" (you can mark up to 3 "solutions". Please LIKE threads if the provided solution is helpful to the problem.