WORKING!!!!
Patched... same problem on launching : FileNotFound
Then uninstalled .Net 4... and (don't know if this is part of the solution) but downloaded the .Net 4 client framework from Microsoft's website... and the game worked immediately afterwards. This is after probably running the install for .Net from the redist about 20 times and re-installing the game 3 times.
WORKING
joy!!! Thx for your help! Spread the word, we now know how to kill these bugs!