Three ways to stop recording (in Standard View):
1. Click "Recording Rules" in the program filter box, to get a list of scheduled recordings. Find one that you want to stop, and click "Configure recording", and choose "Cancel Recording".
2. Click "All Programs" in the program filter box. The program that is being recorded should have a blue status icon. If you have many channels, you can select the specific channel that is being recorded, then the program being recorded should be on top of the list. Select the program and click "Cancel recording" button.
3. View the recording, and right-click in the video window, and choose Recording > Cancel Recording. This was what you did, I do not know why it did not work. Are you sure?