I've been thinking about how weird it was that your upgrade didn't work, and I found this thread: http://forum.notebookreview.com/threads/asus-x401a-upgrade-to-ultrabook-status.682599/ I was looking on Cnet too and someone figured this out:
"I ordered a replacement motherboard and they sent me the wrong one with the HM70 chipset. I don't know how to turn off the shutdown, but if you put the computer to sleep the clock resets, so I created a batch file that counts down and puts the computer to sleep every 28 minutes. It works this way, so it doesn't do the hard shutdown but goes to sleep, which takes about 3 seconds, and you can immediately wake it by moving the mouse. I plan to write a java program to count down in the notifications area, instead of having the batch file running in the command prompt which is not so nice."
If you're willing to deal with that nonsense, you can keep using the i5, but due to the HM70 chipset in your laptop and the nonsense that Intel/Asus pulled, the official max upgrade is the Pentium 2030M. And here I was thinking there wouldn't be any problems...