Just started happening to us also (for past month or so). 8300HD on TimeWarner in Texas.
Getting to "Failed to Record" message and also it shows red that's it's Recording, but when you go to watch the shows in the list it's missing.
I think it has something to do with watching Live-TV during scheduled recordings. I will take a took in Navigator thread if that's the proper place.
Living Room Home-Theater:
Epson 8350 1080p Projector (96") / Panasonic TH-46pz850u 46" 1080p Plasma TV
Onkyo TX-sr607 7.2 HDMI Audio/Video Amplifier/Receiver (630 watts)
Panasonic DMP-BD60 Blu-Ray Disc Player / Cisco 8742hdc DVR (TimeWarner)
Harmony 670 - Universal Remote / HTPC (XMBC/Win7-64) Media Server PC
Polk Audio Monitor Series II Speakers (Large 6.1 Matched Separates) / PSW505 12-Inch Sub