We currently show the clear part gui even when the user has chosen custom partitioning, this makes no sense as no matter what disks the user selects he can use all (non filtered) disks in the custom UI anyways. One could argue that the boot drive selection there still has some value, but that can be done from the bootloader screen which we always show in custom partitioning mode too.
*** Bug 620941 has been marked as a duplicate of this bug. ***
anaconda-14.16-1.fc14 has been submitted as an update for Fedora 14.