If you receive error message after selecting output format (Save as option) and clicking Save button, please open Settings -> Preferences -> Video menu and disable Intel hardware acceleration and/or NVIDIA hardware acceleration.
Most likely you're using outdated or corrupted version of video driver which affects the conversion process.
You don't need to worry about recorded file - in case of receiving error message you can simply close Screen Capture preview window in order to adjust the settings mentioned above.
You can open the recorded file later and save to media format via Capture -> Open Recording File menu.
If the problem does not arise after disabling Intel hardware acceleration and/or NVIDIA hardware acceleration, please download and install the latest version of Intel HD Graphics driver and/or the latest version of NVIDIA videocard driver, then try enabling Intel hardware acceleration and/or NVIDIA hardware acceleration and try saving video again.
In case hardware acceleration options were not initially available, please contact the Support Team so that we could assist you with resolving the problem.