Can't load modules from readonly filesystem

Hello,
I somehow made my own bootcd from Debian Unstable 
with kernel 2.6.6. The bootcd boots up almost normally.
However, during the module loading step, modprobe cannot
load modules because I use read-only filesystem.
The following is the output of "modprobe 8139too"

WARNING: Could not open '/lib/modules/2.6.6/kernel/drivers/net/mii.ko': 
Read-only file system
FATAL: Could not open '/lib/modules/2.6.6/kernel/drivers/net/8139too.ko': 
Read-only file system

I don't understand why I get these errors.
Somebody please tell me what I should do to fix this problem.