Open a command prompt and enter:
This will tell you what woke your computer. i htink it might also give some clues as to what is keeping it from sleeping.
From an elevated security command prompt, you can try:
powercfg -energy -output "<full path>Energy_Report.html"
This information, again, may help you identify the culprit.
In my experience, I never have problems forcing the computer to sleep, however, it sometime will not go into sleep on its own. I have been suspicious of MediaMonkey, but I cannot state with certainty that it is the cause.