puzzling message from ps

[Wilhelm Fitzpatrick <rafial@well.com>]

So I just updated my kernel to the latest benh version, using
kernel-package, and I notice that ps displays the following:

{rtc_lock} {__VERSIONED_SYMBOL(rtc_lock)}
Warning: /boot/System.map-2.4.8-pre4-ben0 does not match kernel data.

any hints on what this means?  The System.map-2.4.8-pre4-ben0 appears to
be the very one that make-kpkg packaged up for me...