Description of problem:
Attempted F18 Beta install on a Lenovo T500 laptop.

This had a previously existing F16 install on it, which consumed all of the disk space. The installer reported that there was insufficient disk space to do the install, and directed me to reclaim the disk. However, I couldn't remove partitions or otherwise change the partition table. The "reclaim" button was greyed out, despite my clicking in various places.

 When I selected custom paritioning, and tried to create new partitions, it still told me that there wasn't enough disk space.

I booted a rescue image and used fdisk to nuke the partitions, and the next install attempt went right through.