The issue seems to be this:
2013-02-19 21:15:33 - main - Create a backup of C:\Games\Piranha Games\MechWarrior Online\Bin32\CryRenderD3D11.dll
2013-02-19 21:15:33 - main - Replacing base file C:\Games\Piranha Games\MechWarrior Online\Bin32\CryRenderD3D11.dll
2013-02-19 21:15:34 - main - Failed swapping files!!!
2013-02-19 21:15:34 - main - Exception: The process cannot access the file 'C:\Games\Piranha Games\MechWarrior Online\Bin32\CryRenderD3D11.dll__new' because it is being used by another process.
2013-02-19 21:15:34 - main - Caught exception in completePatch(): The process cannot access the file 'C:\Games\Piranha Games\MechWarrior Online\Bin32\CryRenderD3D11.dll__new' because it is being used by another process.
2013-02-19 21:15:34 - main - Caught an exception somewhere in the patcher. Closing down...
2013-02-19 21:15:34 - main - Exception messages:
2013-02-19 21:15:34 - main - The process cannot access the file 'C:\Games\Piranha Games\MechWarrior Online\Bin32\CryRenderD3D11.dll__new' because it is being used by another process.
It can be different files (had it report on the main executable as well), but the patcher crashes there.