The command ‘rc-update -u’ may output Clock skew problem even if clock is currently synchronized:

#rc-update -u
* Caching service dependencies … [ ok ]
* Clock skew detected with `/etc/init.d’
* Adjusting mtime of `/lib/rc/init.d/deptree’ to Wed Apr 27 19:01:47 2011

Perhaps it is because clock skew was really big during boot process before time sync has been done ??

(from redmine: issue id 614, created on 2011-04-28, closed on 2011-05-02)