I upgraded from 11.10 to 12.04 (64bit).
after the upgrade Crashplan no longer works. It gives an error of getting "disconnected from the backup engine". Backups no longer take place.
I also had a Canon iP4600 attached to my Ubuntu computer that I was sharing via samba. Now printjobs get stuck in the queue, processing forever.
All these things worked fine in 11.10. I then did a clean install of 12.04, but no change. I searched everywhere but can not find solutions to these problems. I conclude that these must be bugs in 12.04.