CONFIG_BLK_DEV_VIA82CXXX Disappears! - Why?

["Thomas H. George" <xyz@spininternet.com>]

I have learned that I cannot enable DNA unless my 2.6.8 kernel is 
compiled with CONFIG_BLK_DEV_VIA82CXXX selected but the option to make 
this selection has disappeared in make menuconfig.  This happened once 
before and, when I learned what was missing, I found a backup version of 
.config which contained the option.  I have saved that backup and so can 
recover by recompliing the kernel but I don't understand why this 
happens.  In the backup version of .config there are 40 entries under 
IDE chipset support/bugfixes.  In my current .config there are only 9.  
I have made changes in .config but nothing that I believe should have 
unselected and removed CONFIG_BLK_DEV_VIA82CXXX.

I can repair the damage but would be very interested in a better 
understanding of why this occurred.

Tom George