On an Intel Tylersburg EP A0 / Nehalem B0 SDV, with one ~80GB HD and one ~300GB HD (SATA), I first installed a RHEL5.2Snap7 x86_64 and i386. I made two /boot partitions for 32- and 64-bit installs, and a swap partition on sda, and root partitions on sdb1 and sdb2. Then I installed F9 Preview i386 with root on sdb3. Then I tried installed F9 Preview x86_64 with root on sdb5. When I chose "write changes to disk" it thought for a couple minutes and then reported a fatal error trying to format the root partition. I had to reboot. Coming back in the second time to anaconda, the sdb5 partition existed and was listed as "Linux native" rather than the expected "ext3" type. I removed the partition and recreated it, and this time the install worked. I had the same problem when I installed F9 Beta on the same box earlier. I will try to watch for this in the future and see if I can narrow down the conditions under which it occurs. This drive had probably never been formatted before, and this would be the first time those 20GB had been used, where I created sdb5.
*** This bug has been marked as a duplicate of 439633 ***