I am running an Aja Xena LH and capturing through CS4. A few weeks ago whenever I captured video for a class I am in, I would get an error that the data rate is too high. The captured video noticeably had dropped frames and the audio is sped up.
I went ahead and updated CS4 and installed the latest driver provided AJA along with the quicktime driver they offered at their site. Now I can capture between 5-8 minutes before it does the same thing with the exception that is there is no error for data rate being too high and the video/audio isn't affected until after the 5-8 minute record time.
Up until a couple weeks ago it could capture up to an hour of video without a hitch. Checked and I have 100 gigs of free space for capturing.
With the exception of the updates, everything is the same. Screen captures of the settings on CS4 and Machina were made before the updates and were checked against them to ensure they were correct.
I will defrag the drive at first opportunity to see if that that works. I am not the only one who uses that particular computer for capturing so a lot of files get deleted after they are transferred to portable drives. (this is part of a student television station).
Another thing to try, since the problem shows up after 8 minutes, try this:
take that single hard drive of yours and mount it in a stand, card and motor up, magnetic or lid side down. Fan the card with plenty of cool air. Fan the lid side with plenty of air at body temperature. If the fading on the next recording try doesn`t get as severe then you`ve demonstrated that the hard drive is getting weak in the typical way.