Hi wolfmandimitris and welcome,
Are the ripped files able to be played from the hdd?
Most any software player should be able to do this.
If you're having trouble, try VLC.
It's freeware and will play almost anything.
Additionally, it does not rely on outside codecs.
There's link in my sig.
If no luck with the above, try selecting your hdd as your Target and not your burner.
Does this occur with specific, "problem" movies or does it appear to be random?
You can also try Customize mode and select the main title and the audio track and any subtitles you wish.
This should give you similar results as compared with Main Movie mode.
If the files are intact, you should be able to burn them.
Unfortunately, error 400 is a general transcoder error and doesn't really tell us much.
Are there any other details in terms of the error ?
What happens after you receive the error?