Nand CRC errors/warnings

Hi, I'm new to using the BeagleBoard and I have a couple questions to ask; sorry if these questions have been asked and answered before; I tried googling for answers but couldn't find them.

My first question is: Why are there so many nand error messages when Linux kernel first boots up
I kept on getting messages like:

...
Empty flash at 0x06bf64c4 ends at 0x06bf6800

and messages like:
...
JFFS2 notice: (242) check_node_data: wrong data CRC in data node at 0x01981800:
...

It seems like I can save data on the JFFS2 partition but those messages aren't really reassuring. By the way, I used the default kernel (2.6.22-18) posted on Google BeagleBoard support group.

Thanks.

Regards,
Andy