I am one of those users who cringe whenever I encounter software that tries to be cute with error messages. Having worked in the IT industry for many years, I've had it hammered home home that whatever I think is cute will inevitably annoy someone else - particularly with repetition.
Would it be possible to allow the end user to select between cutesy error messages and ones that are, I dare say, a bit more professional in nature? This is otherwise a very nicely thought out software package.