Strange WMC problem-Can't find help - See details inside, please

Ok, this problem started happening a few weeks ago. I've googled and can't seem to find anyone having similar issues.

Whenever I watch something I've recorded (under Recorded TV), it works fine. It records fine, and plays back just fine, too. However, after having watched something that was recorded, WMC won't play other types of files. For example, I go in to my video library and try to play anything (these are either avi or mp4 files), it won't play. When I click on a file, it plays the little sound to indicate that I've selected it, but it just never begins playing. I can continue to navigate around menus, etc, but it won't play anything else. I have to exit from media center back to desktop and re-launch it before it'll play "regular" files again.

Something else that's odd about this is that it does the same thing if I attempt the same steps on my xbox 360 (which is set up as a media center extender.)

One more thing I just remembered - once I go in to Recorded TV, I don't actually need to *play* a recorded TV show, I just need to interact with it for the problem to happen. For example, I can go in to Recorded TV, delete a recorded show, and then the problem with the other media files happens (both on the 360's MC interface and on the WMC computer itself.) The problem once again won't correct itself until I exit media center (back to desktop on the PC, back to dashboard on Xbox 360) and launch WMC again.

Here's the info on my media center computer, TV tuner, etc:

Here is the actual computer that is my WMC
It has 4GB RAM and a 64gig SSD as it's boot drive
I have a 1TB external USB 3.0 hard drive that is dedicated to recorded TV storage
The TV tuner is a Silicon Dust HD Homerun dual tuner (I don't have the model number handy at the moment, I can add it later.) It is a networked unit that is hooked to an OTA HD antenna

This is running on Windows 7 Pro 64 bit.

My "other" media files are stored on a server elsewhere on my network. This whole setup has worked flawlessly for quite a while. This comptuer is dedicated as a media center. It isn't used for any other task.

I'm sorry I don't have the system specs posted as suggested - I'm at work now and don't have access to my media center unit from here. If need be I'll post the system specs using the Systeminfo.exe as recommended.

If anyone has any suggestions, I would love to hear them. Thanks!

That's a tough one. Do you have any codec packs installed? Have you tried moving your "other" media files to a local storage drive?

You might want to go post your question on TheGreenButton.

I did have a codec pack installed to allow me to play .mkv files on my media center computer, but that's been there and unchanged since February of this year.

I have not yet tried moving any of my avi's or mp4's to one of the local drives. I'll try that to see if I continue to have the same problem. The shared drive mapped to my server at home, though, is another of those things that has been set up and working since I set this unit up.

One time, I did have a corrupt file that was causing issues - it would cause MC to crash to desktop. I found and removed the offending avi file and that cleared it up.

Other than that, this machine is pretty much unchanging. The only changes that happen to it are windows updates and antivirus definition updates.

Thanks for the tips. I'll also checkout TheGreenButton.