I work for a public library. We have a Laptops Anytime Kiosk that dispenses 12 HP EliteBook 8470Ps (Windows 7-based) to our patrons for in-library checkout. The AC adapter is plugged in while they're inside the kiosk and they have an extended life battery on them. The laptops run for our entire hours of operation.
Most, if not all, of the machines will sporadically go into a deep sleep mode while inside the kiosk; no button presses or keyboard taps will awaken then when they are like this. The only thing we can do is a hard reset. All of the laptops have deep sleep disabled and all the power settings set to "never turn off." Each of these have Deep Sleep disabled in the BIOS and are set to power on when A/C is detected. So, if they are turned off by a patron, they will turn back on when inserted into the machine.
I've talked to HP numerous times about this and have received the generic "update the BIOS" type suggestions. I did this on one of the laptops and shortly afterward the problem came back again. I thought I'd throw it to the experts now.