I have heard about the fixed/removable attributes of CF cards before and was a bit worried that this was the case here, since changing the MaxTransfer rate didn't solver the problem. However, I swapped the card for a Transcend 4GB card and it seems to be working perfectly.
The card I was using before was not actually a CF card. It was a Sony MS Pro Duo in a MSPD -> CF adapter. This same combo refused to work in my EFIKA, so I assume it's not quite compatible enough.
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moto