Have you tried formatting your filename in different ways?
For example, you could pass in a complete file path, along with 'file://'.
L<file://this/is/your/file>
This could, if it works, come with advantages and disadvantages. The advantage is having links that work in your HTML POD, but the disadvantage seems to be the extra hassle of putting in long file paths.
It's just a thought. Enjoy.