Looks like SD cards are NOT SUPPORTED, although some will work if they are compatible with MMC (however, its maximum size would be 1 Gig)
From iRex FAQ (
http://forum.irexnet.com/viewtopic.php?t=4 ) :
07. Hardware - IO Devices
Which IO Devices are supported?
The iLiad supports most CF, UBS and MMC-cards, however SD cards are not supported. In many cases SD cards can be used since they are compatible with MMC, however the maximum size of an MMC is 1GB. SD cards can be bigger but these can not be used in the iLiad since the addressing method is different than MMC in that case, the maximum size of compatible SB cards therefore is limited to 1GB.
08. Hardware - Internal Memory
Can the 128 MB internal memory be upgraded ?
This is not foreseen. We suggest to use MMC (up to 1GB) or CF (up to 4GB).