PortableAppsPlatform.exe file is not a valid PortableApps.com release and cannot be launched

Today I started getting this message:

PortableAppsPlatform.exe file is not a valid PortableApps.com release and cannot be launched

I couldn't figure out what had changed or why it was complaining after working seamlessly for so long. I could launch the launcher by going to it directly but not otherwise -- and even then it didn't run correctly.

I tried re-installing but to no avail.

Then turned out the solution was to "run as Administrator".
Strange how all of a sudden it required this additional step to work correctly...

UPDATE:
The key lies in permissions in your C:\Users\*\AppData\Local\Temp folder
A windows update resets the permissions. If you give yourself full permission, everything starts working once more!
No need to "run as Administrator"