I sometimes lose access to the hard disk on my HDR2000T, especially after it's been unplugged. Try this if you haven't already.
1 Unplug the recorder at the mains (note, the dc plug/socket contact can become unreliable if the plug is repeatedly taken out/pushed in).
2. Switch on your tv so you can see the Humax Loader screen on startup.
3. Plug in the power supply (assuming it's already plugged into the back of the Humax). You should get the Humax Loader screen as the software starts up and eventually the tv picture should come on. Check to see if media access is available from the hard disk; if not, put the Humax into standby using the remote and wait 2 minutes.
4. Use the remote to turn on the Humax again. You should see the Humax loader screen again and shortly afterwards you should hear the hard disk spin up. Wait until the tv picture comes on the try the media again. On my HDR2000T, when the power is first plugged in the software doesn't seem to fully load but switching to standby then back on seems to correct this and the disk can then be accessed.
Hope this helps; if not it sounds like a major failure of either the disk or elsewhere in the disk system. Smaller Humax disks are available on ebay for less than £10.00 and are easy to fit, needing just a Philips screwdriver.