I'm taking a stab in the dark here (pun intended)... do you happen to have a /run directory?
I had some issues with devices not being detected on boot recently which turned out to be related to udev attempting to read from /run. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=621036 In my case I removed /run and everything was back to normal. If you have no /run then sorry for the dull response.... :)
