Some time ago I installed Ubuntu 12.04.2 from the alternate CD, and choose the option of full-disk encryption. Now I tried to install the proprietary FGLRX driver, but the system lost power halfway in the process, and now the system hangs with a purple screen after I give my pass-phrase. I'm trying to boot from a older kernel, but can't get the GRUB menu to show up pressing SHIFT as recommended in the answers to a similar question. As my system is encrypted, I think it may have something to do with it. Do I need to press SHIFT after or before typing the pass-phrase? I tried both ways and none worked.