Posted 06 February 2011 - 09:12 AM
My understanding is that when you set a time to stand by or hibernate, if there is any running process on the system that cause the CPU to use 10% even for a split second (like you would observe in Task Manager), the timer gets reset back to zero.
The system has to be "idle" and that also means no keyboard, mouse, email reading, surfing, etc. Idle means idle.
Knowing that, if you have something running in the background like an automatic scan, updates, something that is running that periodically checks for something to do, updates, etc. that could use 10% of the CPU - even for a split second, that will reset your timer.
In my notes, I have this reminder to myself from past experience of things that can interfere with a timed stand by or hibernate:
Does your system have installed Windows Search, Skype, iTunes, MagicJack, RSS feeds, any kind of Instant Messenger, any kind of malware scanners doing scans or doing automatic updates like MSE, AVG, Norton, McAfee, Bit Defender? Did a cat walk on your keyboard?
To test, set your options so some small amount of time - maybe 5 minutes and see if the system works properly every time. Be sure the mecahnism itself is not flawed. If it does work properly every time with a short timer, and you set it back to 45 minutes and sometimes it works and sometimes it doesn't work you will have to figure out what is going on that resets the timer.
I think I would set it to 45 minutes, note the time of day and find something else to do for a while - don't touch the system. If the system does not behave in 45 minutes, then look in the Event Viewer from the time you wrote down at the beginning of the watchful period until the current time when the stand by was missed.
Look in the Event Viewer logs for the last 46 minutes and see if you can spot what background process might have woken up and done something. Hopefully, when whatever it is wakes up and does whatever it does, it will put something in the Event Viewer log and you can see what it is.
The mediocre teacher tells. The good teacher explains. The superior teacher demonstrates.