SL-5600 and Pretec SD card

Hello everyone,

I'm experiencing big troubles trying to use a 128MB SD card by Pretec on a
Zaurus SL-5600 either with Sharp or OZ images. Upon insertion, sometimes
the card apparently seems to work properly, but after a while, or after
one tries to copy a large file onto it, it stops working and lots kernel
messages get printed, such as the following:

  mmc read checked internalbuf: ERROR adr = 42391552 (0x286d800) , len =
        1024 (0x400)
  [SD]-R 286d800 0400 ERROR!
  pxa_sd_receive_chars:  wait full FIFO time out by jiffies (cmd=18
         block=26[32k])
  sd_read_multiple(1) : receive error
  mmc read checked internalbuf: ERROR adr = 42392576 (0x286dc00) , len =
       1024 (0x400)
  [SD]-R 286dc00 0400 ERROR!
  SD read CRC error
  sd_read_multiple(1) : receive error

When this occurs, extracting and reinserting the card doesn't help, but if
I keep it off the Zaurus for a while, it starts working again.

I also tried reformatting the card with fdisk to no avail.

Basically, I don't know how to determine if this is just a compatibility
issue, or something (the card, hopefully) is actually not functioning
properly.

Could anyone help?

Thanks,

Max