I've been reading this forum for a good while as I have hx4700 and several issues with the device.
Finally I've found a 'patch' that can handle the SDHC cards in the device too, called Ångström (http://www.angstrom-distribution.org/), works nicely with 8GB SDHC class 6 card as well as 8GB CF card after CF has been partitioned to less than 2G for fat at the start.
There are some glitches here and there but the system has been 'on road' for 4 months now with just random wlan issues.
Posted in this thread as the problem seems to have much attraction and google gave this thread as first 'sane' hit.
Better suggestions to get the device full blown under proprietary firmware are always welcome, though I think I'm happy with current situation, opie is the way to go