Critical Error: yourusername does not own this game

[magitsu]

If you got today greyed out new game etc. buttons and warning "Critical Error: yourusername does not own this game" it might be due to Steam's maintenance on certain accounts. Because that phrase according to Google has only surfaced once, in 2011. http://forums.steampowered.com/forums/showpost.php?p=22706189&postcount=26

Solution for that might be to just wait for Steam to do their thing. Though this is conjecture, no idea if there is any maintenance actually going on. CO should try to find this out if this issue doesn't go away soon or gets many affected.

First sighting for Cities: Skylines: http://steamcommunity.com/app/255710/discussions/0/610574827758374707/

It actually seems a bit quirky since his on his HTPC the game supposedly works. So it's not account-related issue but account+associated hardware?

I've tried admin, I've tried setting permissions, I've tried installing on the C drive, Re-Installing Steam, Re-Downloaded 3 times, Verfied the Cache many many times...
Found a log within the Cities Skylines install folder which says Critical Error: DragonSlayer does not own this game. Yet I've been forced to play this on my HTPC (not comfortable at all) at it works fine. Both are 64bit Windows 8.1. Looked on the offical dev forums and others have same issue with no fix yet found
Its like the games assets are not loading as both start new game and load are both greyed out and I cannot create maps and stuff as no data is avaliable. Then to top it off it does not keep me logged in and when I quit the game it crashes.