This is happening to me as well...I know for absolute certainty it's becuase I switched to Windows 8.1....running as adminstrator...ran shortcut exe as adminstrator, tried running it in compatibility mode for 7 and 8.....and of course tried the added argument suggestion posted in a few places. I either get something about a child process error or nothing at all depending on which 4gb patch I'm using, it's location, and whether or not I am running as adminstrator (despite being an administrator account *rolls eyes*) The patch works fine outside of MO though...along with loading NV in any other way. I also can use NVSE through MO...but I quickly run into out of memory errors without the increased memory.