I have a situation where we have LANDesk in place for management. Recently, we pushed a policy using the built in Power Management tools where the system would go into screensaver mode after 15 minutes and then sleep after 30 minutes of inactivity. The problem is, when the computer sleeps during the day, it will wake up without a problem. However, if the machine sleeps overnight, the user will have to cycle the power to get it to come back.
The LANDesk administrator states that there are no reoccurring jobs that happen overnight.
The affected computers are a mixture of Dell 620/745/755s running XP. I haven't had anyone running Vista mention they're having a problem, but that could be a red herring since I don't have that many Vista machines deployed.. The BIOSs have been updated to their current levels and some have had their NIC drivers patched to the latest from Dell.
In the BIOS: Wake state has been set to S1. Wake on LAN has been set to On.