It is interesting what both of you have in common. Royce has the problem every midnight and Vicki at 5:45PM. Which would lead one to believe that something else is occurring at those exact times which affects the SQL Server Amazing Charts service. While one would think that it would be the AC Backup, there are two things that argue against that. First, as you stated Royce, you changed the time, and second, quite a few people use the backup program and haven't had that issue. The backup program does not work by stopping and starting the service.
If you look in Control Panel -> Scheduled Tasks, you may notice something starting at that exact time. Check Windows Updates and see if it is on automatic. If so, shut that down.
Finally, I am running SP2 for a service pack on SQL Server Express 2005. They now have SP3 out. I don't know if that would help. My guess is it wouldn't.
