Cheers again for your help mate.
Well last night I restarted the computer during that clear NVRAM thingy and after trying to boot into safe mode, which it wouldn't do, I bit the bullet and inserted the DVD and tried to re-install off the DVD again. Went to the same screen for ages, and didn't think it would work, but eventually, the installer kicked in. Went through the install and it worked. Now boots up fine. Remembers all my settings, including the changes I made to dashboard.
Bit reluctant to run the upgrader now... might wait until 10.4.3 comes out and leap frog over the 10.4.2...