Creative Cloud cannot update itself:
What now?
Internet connection is fine, computer is absoluuutely fine. No other problems.
Using Windows 7 x64, running as non-admin, UAC enabled, scanner is Avast 2014, internet pipe is 100Mb fiberoptic without outgoing firewall.
/edit
WTF. Frustratingly, this update mechanism hijacks the cloud application. I cannot choose not to upgrade.
/edit2
More info. Whilst UAC is enabled, the updater does properly elevate itself. Disabling the scanner doesn't help either.
Also, it does put a shortcut on my desktop, so it does get to that point in the update process. This also hints that the failed update doesn't even revert things properly. Which is yet another thing for Adobe to fix.