Micro SD read/write not working on AT91RM9200

Hello,

I have a board with AT91RM9200 SoC. I am trying to write a test to use
Micro SD card on this board.
I am using MCI interface to use Micro SD card.

The initialization commands are working correctly for the Micro SD
card. I get all the parameters back after the initialization commands.
But the read/write operation are not working for the card.

I am using polling method to wait for the completion of read write
command. I am using exactly the same method as described in the
AT91RM9200 data sheet (sections 33.7.3 and 33.7.4). But the TXREADY
and RXREADY bits in MCI_SR never get set after I issue a read block or
write block command. Instead, I get UNRE and OVRE bits set in MCI_SR
register.

Can anyone tell me why I get these errors, and what is the possible
solution for that?
I am using the sample code downloaded from Atmel website as a base for
my development.

Thanks for any help in advance.

Bhavik