One of those nasty interoperability problems.

You're dealing with firmware in the card, which runs the host
communications and the flash translation layer (FTL).

The compliance against standards varies considerably across the
market.  My guess is you've found a bug in the firmware, a corner case
that is exercised by your pattern of access, but is not tested by the
device manufacturer or firmware vendor.

Some ideas:

- switch to a pattern of access that is known to work,

- randomly experiment with patterns of access until one might be found
  to work,

- raise issue with the device manufacturer, who will escalate to the
  firmware vendor,

- explore the various documented instances of firmware upload
  processes, in case you can find one that gets you more options.

I'm more familiar with using SD host controllers with these things.

Perhaps the card wants a supply voltage change; some SDHC or SDXC
cards require 1.8 V at higher transfer speeds.

--=20
James Cameron
http://quozl.linux.org.au/
--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.