I received my Herotab C8 a few days ago and have experienced a similar problem. After putting it to sleep with the power bottom I could wake it up by pressing the Home button in the front but after some casual use I put away the tablet after putting it to sleep in the same manner, left it for an hour or so, came back and press the Home button and nothing happens. Pressed the power button - nothing. Finally had to press and hold the power button and it starts booting up. Came up fine though, except it took a good half minute so I had to wait for it to boot up before I can use it. Everything's working (except I had to re-enable WiFi again). Use it for a little bit and left it on my desk for an hour or two. Came back and found it had powered off itself again and I had to press/hold the power button to boot it up again.
I read this thread about the 3G monitor background service and decided to try that. Found the service and stopped it. Didn't work. Left the C8 in sleep mode for an hour or two and it shuts off.
So finally, I decided to bite the bullet and flash it with other ROMs (mind you, I was hoping that the C8 would have worked to my satisfaction right out of the box, especially because it came with 2.3 already and market worked fine). I tried a few including C8lean, PhoenixMod, simplistica, Pryanik, M7++0805, but all of them exhibit the same exact problem of the tablet self powering off after a period of unuse. So finally I flashed it with the stock 2.3 ROM again and the problem persisted.
I don't know if I have just received defective hardware or not but I have sent an email to the merchant (bought mine from Amazon - merchant is LL Corporation) last night to ask if I can get an exchange - haven't heard back yet.
I really like this tablet - right price, right size (10" too big for me to hold and carry around). I mainly wanted a ebook reader and if it can play a game or two from time to time and also double as a note taker or personal journal that fits my bill. However, this random self-initiated powering off really put a dent on the otherwise wonderful experience.
Is anybody else having the same problem? Any other suggestions for fixes?
Thanks in advance.
-cf-