I went out to the observatory again on Friday and had another go at making the DBBC boot Linux off our 8GB CF card.
Investigation of the hopeful error message which was observed previously revealed that instead of being useful it is a generic “confused hardware” message. There seems to be no good reason in the images' configuration for these problems. Extensive tweaking of bios settings (ACPI off, DMA off, etc) did not improve the situation.
My feeling is that before I spend more hours struggling with this, that we should buy a cheap 4GB CF and see if we have more success with this.