Description of problem:
I attempted to install F18-TC4 in place of an old F15 installation.  In the custom partitioing screen I selected the preexisting /boot and / partitions and entered those same mount points and hit apply changes.  The F18 tree then showed those partitions inside.  I hit done.  No other changes were made to installer defaults.  Proceeded to the next step.  Screen prompts for a root password, but an error windows pops up not more than 5 seconds into the installation process.

Version-Release number of selected component:
anaconda-18.16

Additional info:
libreport version: 2.0.14
cmdline:        /usr/bin/python  /sbin/anaconda
kernel:         3.6.1-1.fc18.x86_64

description:
:The following was filed automatically by anaconda:
:anaconda 18.16 exception report
:Traceback (most recent call first):
:  File "/usr/lib/python2.7/site-packages/rpmUtils/transaction.py", line 58, in dbMatch
:    mi = self.ts.dbMatch(*args, **kwds)
:  File "/usr/lib/python2.7/site-packages/yum/rpmsack.py", line 1212, in _get_packages
:    mi = ts.dbMatch(*args, **kwds)
:  File "/usr/lib/python2.7/site-packages/yum/rpmsack.py", line 1258, in _search
:    for hdr, idx in mi:
:  File "/usr/lib/python2.7/site-packages/yum/rpmsack.py", line 1193, in searchNames
:    returnList.extend(self._search(name=name))
:  File "/usr/lib/python2.7/site-packages/yum/__init__.py", line 4480, in install
:    ipkgs = self.rpmdb.searchNames([po.name])
:  File "/usr/lib/python2.7/site-packages/yum/__init__.py", line 3597, in selectGroup
:    pkg_warning_level='debug2')
:  File "/usr/lib64/python2.7/site-packages/pyanaconda/packaging/yumpayload.py", line 946, in _selectYumGroup
:    self._yum.selectGroup(groupid, group_package_types=pkg_types)
:  File "/usr/lib64/python2.7/site-packages/pyanaconda/packaging/yumpayload.py", line 1053, in _applyYumSelections
:    self._selectYumGroup("core")
:  File "/usr/lib64/python2.7/site-packages/pyanaconda/packaging/yumpayload.py", line 1097, in checkSoftwareSelection
:    self._applyYumSelections()
:  File "/usr/lib64/python2.7/site-packages/pyanaconda/packaging/yumpayload.py", line 1176, in preInstall
:    self.checkSoftwareSelection()
:  File "/usr/lib64/python2.7/site-packages/pyanaconda/install.py", line 111, in doInstall
:    payload.preInstall(packages=packages, groups=payload.languageGroups(ksdata.lang.lang))
:  File "/usr/lib64/python2.7/threading.py", line 504, in run
:    self.__target(*self.__args, **self.__kwargs)
:  File "/usr/lib64/python2.7/site-packages/pyanaconda/threads.py", line 91, in run
:    threading.Thread.run(self, *args, **kwargs)
:error: rpmdb open failed