Comment 5 for bug 766292

I never had problems during the installation. And for various reasons, I have done both a completely new installation and an upgrade from a previous 10.10 version. The problem was that my system had some random crashes at startup (sometimes I was able to start the system) with a message similar to what you report.
Anyway I think you can pass the option "radeon.modeset=0" during the installation. At start of Live CD, when you choose the language, you can also specify some additional parameters to pass to Linux kernel (It should be by pressing F6, if I remember correctly). The trick is to pass here the parameter specified above, so you should be able to perform a complete installation of the system.