Description of problem: /dev/sda1 was my prior '/boot'. anaconda autopartitioned it to be a new /boot. At some point in doing so, nautilus mounted it. Ergo, mke2fs failed, and anaconda pops up: 'An error occured trying to format sda1. This problem is serious, and the install cannot continue. Press <Enter> to exit the installer.' Version-Release number of selected component (if applicable): rawhide-Developer-20071025
Does it work if you lock hal manually using hal-lock(1)? lshal --monitor should also show when someone takes the lock...
anaconda's using the wrong path to see if haldaemon is running. Fixed in CVS...
Fix confirmed by doing an install with rawhide-20071028 x86_64 live image with preexisting install on the disk