OK, so lets have a quick round of what could go wrong post-upgrade to Ubuntu Jaunty and how to fix it, fast. These are some of the problems I faced, and found all the solutions by googling. Just listing them out here. Hope this helps some of you.
1. Proprietary ATI drivers
The first thing we come across is the video drivers which never were. The moment you try to install proprietary ATI drivers for “old” cards (my ATI RadeonExpress 1250 happens to be one of those), you will get a system freeze. No graphics, no inputs, just some random colors on screen, which aren’t very pretty either.
Solution here:
sudo /usr/share/ati/fglrx-uninstall.sh # (if it exists) sudo apt-get remove --purge fglrx* sudo apt-get remove --purge xserver-xorg-video-ati xserver-xorg-video-radeon sudo apt-get install xserver-xorg-video-ati sudo apt-get install --reinstall libgl1-mesa-glx libgl1-mesa-dri xserver-xorg-core dpkg-reconfigure xserver-xorg
You could probably create a script of this sort and save it in your home directory, so that when the system does fail, you can easily get into recovery mode (use the “Recovery mode” listed in Grub) and just run this script rather than attempt googling through Lynx, which I almost always end up doing. In case you plan to run this script in recovery mode, you don’t need the “sudo” command for any line since you will be “root” already.
2. Screen Freeze with Compiz
The open source drivers you install for ATI are known to create hassles for 3D graphics. Jaunty does allow you to enable Compiz (System Appearance -> Effects -> Normal / Best). However, I had a complete system freeze lot of times while I gave Compiz a try. I could easily reproduce the strace gedit bug while 3D effects were enabled.
Solution: Disable Compiz (or downgrade 
)
3. VirtualBox fails to start
The Virtualbox kernel module needs to be recompiled for the newer kernel in Jaunty. This problem is not specific to Jaunty (or even Ubuntu), but no harm in listing it here.
sudo apt-get install linux-headers-$(uname -r)
sudo /etc/init.d/vboxdrv setup
The first line downloads appropriate Kernel Headers for the latest Kernel, which will be used by the “vboxdrv setup” command.