I'm wondering this as well. i think the videos directory is wrong in mythweb. I have to test more.
If you have multiple tuners in different machines, I don't know of an easy way to correct the mythweb error.
In Mythweb, the directory for the recordings is a symlink in the /var/www/mythweb/data directory.
/var/www/mythweb/data/recordings -> target_link
With 7.10 RC2, it's using the default MythTV directory (/var/lib/mythtv/recordings). So that's definitely going to produce the file does not exist error.
If you only have one machine with tuner cards, you should be able to delete the recordings symlink and create anot1her on the core:
sudo rm recordings
sudo ln -s /home/public/data/videos/tv_shows_1 recordings
In my case, I have a core/hybrid and a md with a tuner card, so my recordings show up in tv_shows_1 and tv_shows_57, not sure how I would make the web download link work for me...