Some day, this thing stopped to work for me. I was not aware of doing anything what could break it, even any related package was not updated. Time went on and I still did not find time to learn how to debug this udev/hal/dbus/gnome-volume-manager machinery.
Today, after some googling I found short debugging guide on Ubuntu wiki, which quickly revealed me that "volume.ignore set to true on /org/freedesktop/Hal/devices/volume_uuid_4717_5407, not mounting". Well I didn't configure anything to be ignored, so let's dig deeper in this.
As I had no idea where this thing could be set, I again started to google and /etc/hal and /usr/share/hal seem to be the right place where to start grep. Nothing related in /etc, but too much entries in /usr. However most of them were selective for some special USB disks or partitions. But there was one which did this unconditionally - it was file /usr/share/hal/fdi/policy/gparted-disable-automount.fdi, what crap from gparted. Now I remember that I used this for formatting and partitioning something on USB and after doing all job, it crashed. So it left this piece of HAL hack inside /usr/share/hal and it was cause of anything not mounting.
Seems to be worth of reporting as a bug... Wait a moment, it's already known and some patch for it exists. Hopefully we will see this soon in unstable.