For other people finding this thread, you should just have to wipe the exes.hogg and gameclient (the DLLs don't hurt). I wouldn't delete the cache folder, since that will trigger a shader recompile that can take a while.
Well I have renamed exes.hogg and gameclient.exe by adding the suffix .old to each, I then restart the launcher with a force verify and I am still getting the unable to start game client: %1 is not a valid win32 application. I have also made sure that gameclient .exe is checked to run as administrator as well as the launcher.
This is a Win7 64bit OS. It was running fine until the patch this week. Then I started getting corrupted hogg crashes. I renamed the bins.hogg file and then forced verify, and it let me get in the game for all of about 2 minutes, then I started crashed out again with the corrupted hogg error. Since then I have not been able to get back in the game with this error at the launcher, or crashes during the force verify.