Well, I think it's kind of an underestimation of how severe the "slow media" error is. Jon Tatooles has a long thread on what "slow media" means at this link:
What the manual says is:
Failure During Recording
In the event of a storage media failure, the specific error will be indicated on the LCD and warning bells in the headphone monitor. Possible causes of media failure include, a hard drive in severe motion which results in recording errors, a CompactFlash card filling up while recording, or an external DVD-RAM that can’t keep up with the chosen data rate, track count, or file type. If more than one drive is selected for recording, the remaining drives will continue recording without failure. If a media continues to be displayed as slow after the warning prompt has been cleared, press the Stop key to clear the Slow status.
I think what happened in the o.p.'s situation is, the hard drive was already dangerously filled to capacity (less than 10% open space), and the CF card was too slow, which resulted in losing files. To me, every computer-based recording device in the world will fail under similar conditions. I once saw a $500,000 color-correction computer brought to its knees when it was overloaded with about 95% on all available hard drives, which led to about 2 days of brutal pain and suffering. It's kind of like filling a coffee cup with hot coffee to about 90%, and then trying to run across a football field at top speed... kinda hard to do it without spilling it and getting burned. It's a lot safer if it's only, say, 50% filled.
Maybe in this case, SD could build in a new error correction check routine at boot-up where it went out and checked the available space on the internal hard drive, and then said, "hey, stupid! The drive is almost filled up! I'd advise that you erase some crap first, or proceed at your own peril!" (I love snappy error messages.)