Odd log messages.

Lately I find the following entries in /var/log/warn

udevd[pid]: get_netlink_msg: no ACTION in payload found, skip event 'umount'
udevd[pid]; get_netlink_msg: no ACTION in payload found, skip event 'mount'

Any idea what it might mean? There is an external hdd mounted, which obviously has something to do with it, but I'm at a loss as to what.

Thanks for any help.