Comment 21 for bug 1160346

sudodus, "forcepae" isn't in the mainline kernel yet so it's up to the Ubuntu Kernel team as to whether they add the patch to the kernel now and/or backport it to 12.04. For someone with Pentium M who wants to upgrade from 12.04 the easiest way would be to do the fakepae trick of mounting a modified version of /proc/cpuinfo that contains the pae flag over the original, and then do the upgrade. Instructions for that could be added to the wiki.