My system was initially set up as a Kubuntu Intrepid system, and then changed to Ubuntu (as an escape from KDE4). Since then I have only run the Ubuntu desktop. The stepwise upgrade from 8.10 to 9.04 to 9.10 went well, but failed badly on upgrade to 10.04.
Step1: Upgrade to 9.04:
Step2: Upgrade to 9.10:
Both steps executed without problems. Optically - how the desktop and panels were arranged - and by playing with my standard software, everything was fine. I definitively was running the Gnome Ubuntu desktop.
Step3: Upgrade to 10.04:
A myriad of issues had come up with that upgrade. I'll list a few of them:
1) Only Kubuntu (and xterm) was available after the upgrade; Gnome was gone! I then installed ubuntu-desktop via Synaptic, and noticed that it pulled a whole bunch of dependencies. So obviously the whole ubuntu-thing was eradicated and only KDE left! After installing ubuntu-desktop the desktop and panels were a mess. Apparently the previous theme is absent, and no new one is established by default. Some icons were - e.g. that from firefox - were replaced by the 'missing-icon' icon, although the program is still installed, and clicking the 'missing-icon' opens that application.
2) During start, right before the login screen, the display shows some scrambled color lines at the top of the screen, the audio gives some bop-bop-bop-bop sound, before the correct login screen comes up, and the correct jingle sounds. After that, another round of bop-bops and then screen and sound are ok. During shutdown, the same happens in reverse, i.e. first the scrambled colors at top of monitor, then bop-bop-bop-bop, then shutdown. This never occured throughout all Intrepid times
3) After login some unknown process causes 100% CPU use, of which 50-60% are io-wait states (see attached screenshot: in the middle of the top panel are Systemmonitor displays. The leftmost one has blue for user and red for IO)
4) Also right after login some unknown process is causing sending of bursts of 20-45kbits7sec every 3 sec to the network. see attached screenshot (visible both in top panel - middle window of Systemmonitor - and bottom part of Resources display). It is NOT apt-get or any other update activity; I would expect to see something like this from a virus. Again, I have never seen such before on my system
5) I use mail-notification, which, on other Lucid systems of mine, is popping up a notification about new emails near the top panel. Here, however, the messages appear as dialog boxes (with ok and cancel buttons) in the middle of the screen, and stay there irrespective of preferences I set.
6) gthumb does not recognize any of my many, carefully created catalogues. This had been a lot of work. At least, some import option should be offered!!!
7) my keyboard had been changed from using the grave and acute keys to not using them
8) the top panel icon to logout/suspend/hibernate/shutdown has been deleted. I can only shutdown using the System menu; don't know how to suspend or hibernate
etc.
This is a real mess. Good thing I tried the upgrade from a copy of the partition ;-/
Of course you can't upgrade all the time. You can upgrade from 9.10 to 10.04 or from 8.04 to 10.04 but you can't upgrade from 8.10 to 9.04 to 9.10 to 10.04 and still think that everything will work ;-)
Why don't you just save your few files on an usb stick and do a fresh Lucid install?