You can check the rather cryptic system event log. To do that click Start -> Control Panel -> Administrative Tools -> Event Viewer. Once in Event Viewer click on the system log and scroll through the entries looking for those flagged "error" to see if you can find hints as to where the problem could be.
`
I have to tell you I've upgraded 6 PCs (3 different brands) from 8 to 8.1 and didn't have any problems. Did you make sure you had all the Windows 8 updates installed before attempting the upgrade?
I have a Aspire V5 122P with Windows 8. Got a message that 8.1 is ready. Went to the Store...appeared to download and "Your Windows 8.1 install couldn't be completed". Looked around the Acer site, downloaded the newest BIOS and "Error. Please update to BIOS V2.06 first for critical secure mechanism changed". Is this directly translated from Chinese? Makes no sense. That's exactly what I downloaded and extracted. Looks like trying to get 8.1 on a computer has been a bummer for a lotta folks. Any suggestions?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic