USB storage automounting doesn't work anymore

I am using OpenSuse 11.1 with Gnome and for no particular reason USB storage automounting stopped working. I can mount the USB drive manually, but if I just plug the device, nothing happens. Using Thunar file manager however, the USB device is detected but I get “Cannot obtain lock on /media/.hal-mtab.” , probably because another program has tried to mount the device and failed apparently. I’ve read many people having the same problem but could not solve it. I really don’t know what do to about this anymore.

Thanks for your help