I have checked the website, the software and the support pages, but there is nowhere explained how to overcome that or if it's even considered as being a bug or an error. I recommend choosing the output to another partition than the default one because this can be caused by lack of space and temporary files. If it still doesn't work, then use the link posted below to reach the Contact page where you can see the available contact options.
Contact page: http://www.converterlite.com/contact/
