I had 11.10 x64 installed on AMD 4core with NVidia card. I had problems changing screen resolution. I have just over-installed 12.04 x64. It went well. Screen resolution changes worked well. I ran diskutil(?) which said drive was good but grumbled about misaligned partitions of 1K & 3K. I then applies 60+ updates. It said it needed to restart. I press 'restart' screen button but it wouldn't restart. I pressed the H/W reset. It came up with GNU GRUB version 1.99, 3 lines help text and a GRUB prompt. I pressed H/W reset. Same GRUB prompt again. How do I get the Ubuntu Desktop back? Thanks.
Originally posted as a comment by brewmanz (OP):
I seem to have fixed it. I reinstalled, deleted swap space, added 3MB boot space(?), added swap back in, formatted OpSys partition & kept my big data partition. Applied updates and still boots okay. I guess some of those warnings (something like "no boot partition - you might have problems later") need to be made clearer.