Getting the image complete URL

Hi all,

It is easy to get a product. In the product we can find the internalId for the thumbnail picture. So then I want to get the URL so that I can show that picture. How do I get that URL?

I have tried to just do a general 'get' on the file with internalId of that case, but it gives me:

Array
(
    [readResponse] => Array
        (
            [status] => Array
                (
                    [statusDetail] => Array
                        (
                            [code] => UNEXPECTED_ERROR
                            [message] => An unexpected error occurred.
                        )

                    [!isSuccess] => false
                )

        )

)

I have verified that that specific file do exist.

Anyone with a good example of how to get the url to the thumbnail? Or to an image in general?