Macbook Air 2012 goes back to Sleep immediately after waking it up

Question

So I have had this 13inch Macbook Pro for about a month and in that time it has done this about twice already. In order to get it working again I have to wake it up the second time and then it works fine.
I have done the SMC  and PRAM reset but that does not seem to help. This usally happens when the Mac is connected to a power supply and goes to sleep by itself after some inactivity. Would like to know if anyone is having a similar issue, if so did you found any solution? Thanks in advance. Just to clarify I am working on a 13 inch Macbook Air with 256GB SSD and using Mountian Lion 10.8.

Answer 1

Have also had this issue since purchase. Have tried most solutions, including restoring from a time machine backup file, to no avail.
The issue always happens like this:
1) plug computer in with screen open.
2) macbook air goes to sleep on its own
3) come back to use computer later (usually a few hours later) and take computer off power supply.
4) computer works fine for about 2 minutes
5) computer screen dims for about 2 seconds and then the computer goes to sleep
6) have to hit space bar repeatedly to wake computer up
7) Computer runs normally until plugged in again and then the whole issue starts all over again from step 1.
Anyone help?
Am running 10.8.4. 2ghz Intel Core i7, 8gb ram, 256gb SSD, 11.6" Macbook Air (purchased June 2012)