By default, My Screen Recorder uses the F8 key for record/pause, F9 for stop and F10 for abort. It seems that some other application is already using the F8 key.
To change the keys:
1. On the 'Tools' menu, click 'Settings'
2. Select the 'Keyboard' tab
3. Change to a function key of your choice. You can also combine the Ctrl, Alt and Shift keys with the function keys. Select 'None' from the drop-down boxed if you do not want to set any key.
4. Click OK.