Ubuntu 11.04 is horrendously unstable and should be avoided. In any case if you wanted to carry out a rolling upgrade it can only be done in incremental stages on a standard release. For example you would need to upgrade to Ubuntu 9.10 then to Ubuntu 10.04 LTS then to Ubuntu 10.10 and finally to Ubuntu 11.04
During these upgrades system wide changes take place and it is almost inevitable there would be frequent crashes on even worse the installation would be unusable. Much has changed since Ubuntu 9.04 not to mention Ext3 and grub-legacy being replaced with Ext4 and GRUB2 in Ubuntu 9.10 which remains the same in subsequent releases.
You need to be looking at a fresh installation. I thoroughly recommend Linux Mint 9 LTS which is built upon Ubuntu 10.04 LTS its easy to install and easy to use plus it comes with much of the software you are likely to need preinstalled
Linux Mint 9 LTS Download
http://www.linuxmint.com/edition.php?id=52
Linux Mint 9 LTS Installation Guide
http://www.linuxbsdos.com/2009/12/03/linux-mint-8-installation-guide/
Linux Mint 9 LTS Release Notes/User Guide
http://www.linuxmint.com/rel_isadora.php
You download the ISO. image of Linux Mint 9 LTS then you need to create a Bootable LiveCD for installation
https://help.ubuntu.com/community/BurningIsoHowto
Linux Mint 9 LTS can also be run direct from the LiveCD from Boot without touching your Hard Drive
Once installed I recommend updating to Firefox 5 as Firefox 3.6 comes installed as default
How To install Firefox 5 on Linux Mint 9 LTS/Linux Mint 10 using the Firefox Stable PPA
http://www.webupd8.org/2011/06/firefox-5-lands-in-firefox-stable-ppa.html
LUg.