I'm running the Platform within my Dropbox folder, in Dropbox/Applications/PortableApps.com. When I most recently ran the Platform, it asked me to update, which I did, but the update was deposited a folder down, in Dropbox/PortableApps.com.
Obviously, as a portable app it's not a great amount of effort to shunt the folders around and this doesn't cause problems, but it is equally clearly not how this is meant to work! Not least because if the Platform is in the wrong folder, it doesn't pick up the applications available.
Are other people seeing the same behaviour?
What is the full path to your install? Did you adjust any of the folders yourself? I installed 10.0.1 (last release from December) in the exact same spot in my DropBox folder (Start.exe being in Dropbox/Applications/PortableApps.com on my Windows 7 box) and had it upgrade to 10.1.2 using the updater and it worked as expected.
Sometimes, the impossible can become possible, if you're awesome!