Ok, i am on Windows Server platform. I imagine the same works for for XP. Here's what I did.
Go to Control Panel > Services. Scroll down to Nero Scheduler. Open it up. Go to the Dependencies panel, change the "log on as system account" to "log on as" and enter an Administrator-level account and password. Click "Apply". Then stop and restart the service. Now you can restart Nero and the error will be gone. You will also have access to your backup schedule, etc.
Please post if this helps or not.
Nick in Salt Lake