Hello Glark,
Never edit the podcast information directly in the "custom fields" in WordPress. The data after the 3rd line is what is called serialized, values are stored in a serialized method where the length of each string is used to determine how to unserialize the content. If you edit the content directly and the changes change the lengths of strings, then the serialized data will become corrupted and cause the issue you are reporting.
To edit episode information, go to the Podcast Episode box in the edit post screen, check the "modify" box to expand all of the podcast episode options. Then edit the field in question and finish by clicking update on the blog post to save those changes.
Thanks,
Angelo