PC Video files not showing up on Tivo

I have a Tivo Series 2 DT and am running Tivo Desktop 2.4 plus. The tivo and the computer are running on a wired home network. I have no problem transferring files from my tivo to my pc. Additionally, I am able to play mp3 files from my computer on my tivo. However, when I want to transfer videos back from my pc to my tivo I run into a problem. The pc shows up under Tivo's "now playing" list but when I click on it, 90% of the time the video files do not come up. I simply am left looking at the blue PC screen. The other 10% of the time the files come up right away or on occasion, after a long wait some of the video files come up but not all of them. When it does work, it works wonderfully. I can start watching a file right away and my network is fast enough to stay ahead of the video playback. I have checked my firewall settings and believe that I have everything set correctly. Any suggestions?