I actually re-installed my 11.04 first and configured everything. Then I did a fresh install of 12.04 on a separate partition in a multi-boot config. Then only after 12.04 was fully up and running I made it the default boot option and it is happily chugging along. In case I come across any problem with 12.04 I can simply switch back to my 11.04 partition which works just fine...