It appears that /etc/rc.d/rc.sysinit was recently modified to move calls to
hwclock earlier in the file.
In fact, it appears, that these calls now happen before the root filesystem
is checked and remounted read-write.
This is somewhat problematic, given that hwclock attempts to modify files
on the root filesystem (most notably, /etc/adjtime) when it is called with
Now every time I reboot I get hwclock about how it can't modify what it
wants to modify because it's on a read only filesystem. Alas, I failed to
capture the exact error, but it happens reliably. I suspect you can
duplicate it by removing /etc/adjtime before rebooting.
AFAIK, this was fixed in 6.40-1....