Over the last week or so I've had good luck with pxeboot rawhide installs using custom disk layouts. But yesterday I changed my office machine to an MSI P43 NEO3 and Anaconda was stumped.
Different versions of fdisk showed slightly different partitions. After several attempts to install Rawhide, I gave up and installed OpenSUSE, which installed without complaint. But Rawhide still couldn't hack custom layout.
I tried reverting to the "last known good" Rawhide from last year (anaconds 11.5.0.17) but custom layout still got an unhandled exception.
Finally I swapped hard drives and used Win XP to clear partitions and install Windows on a 50G partition. The current Rawhide was able to install using the "replace linux" option.
I know the details here are rather sketchy. I suspect the problem may be related to the motherboard and the apparent presence of two partition tables on the same drive. And the problem <so far> is appearing only on this motherboard.