Two things spring to mind here, Heat related problem, in that you get intermittent screen interupts after 3+ hours, suggest you give the thing a good clean out inside with some canned air and make sure when you use it that the vents are not restricted and that it is not placed on an insulating material, Duvets make good laptop killers.
Second one, problems entering hibernation, from past experience, suggest you turn off 'Wake on LAN' feature and give it a good clean.
Other than that Acer are probably correct in that it is a software related problem, if you can try using system restore and take it back to a time prior to you having this problem.