So are you using the all-in-one? If not, I highly recommend it since contains the exact, nothing more or less, files required to play fRO. If you are doing so, it could be that the download of it was missing some files. I would download the halloween patch here and unpack it into your RO folder, replacing any files which it prompts you to replace. I have problems directly starting a client via the start button on the patcher, I simply patch and open the client using the .exe application.