And another problem!
When I boot in recovery mode, and don't try to start X, I can't get connected to the network.
If I type "ifconfig eth0", I get a message that eth0 is not detected. The computer has an ethernet connection, with a realtek controller, which should use the R8168 module. With the new kernel (3.0.0-1), that module is not getting loaded. But even with the old kernel (2.6.39-2), the correct R8168 module is loaded, and it still can't detect eth0.
So no graphics, no internet connection : great upgrade!