Problem 1.
Ubuntu Disappearing Unity bar after Upgrade to 12.04
After upgrading to 12.04 and rebooting I noticed that the Unity (sidebar) was missing, I tried a couple of commands to no avail:unity --reset
unity --reset-icons
sudo apt-get update
sudo apt-get install upgrade (i did this as it looked like the upgrade had got stuck and didn't finish)
And then rebooted, alas this didn't solve the problem
The next method that I tried (and worked) was to install additional drivers, in my case i have an Nvidia graphics card, drivers were installed.
After switching to the recommended driver this solved the problem.
Problem 2.
"Buffer I/O error on device fd0, logical block 0" error
Switching to console mode, this error continuously appeared, so as we know this means that its looking for a floppy drive that isnt attached.
Simplest way to fix this is to disable it with
vi /etc/modprobe.d/blacklist
and adding this line
blacklist floppy
And then reboot