Couldn't open directory /lib/modules/2.6.12: No such file or directory

[<KokHow.Teh@infineon.com>]

Hi;
	I am using a debian linux-2.6.17 system to build a linux-2.6.x
(x = 12 or 9). After `make install` the newly built kernel, I could boot
up the new kernel without error. However, when I boot up the system back
to the original default linux-2.6.17, I am stumbled into the error above
and dropped into single user shell where I could type anything on the
keyboard now. My question is, what has gone wrong with any configuration
in /boot that could have miss-led the original default linux-2.6.17 to
load modules from the wrong directories; directories which are supposed
to be used by the respective linux kernel when it boots up?
	Any insight is appreciated.

Thanks & Regards,
KH