Description of problem:
yum can't start because it can't open the rpm database

Version-Release number of selected component (if applicable):
yum-3.2.21-8.fc11.noarch

How reproducible:
Always

Steps to Reproduce:
1. sudo yum shell
  
Actual results:
Loaded plugins: dellsysidplugin2, refresh-packagekit                                                 
rpmdb: Program version 4.7 doesn't match environment version 4.5
error: db4 error(-30971) from dbenv->open: DB_VERSION_MISMATCH: Database environment version mismatch
error: cannot open Packages index using db3 -  (-30971)
error: cannot open Packages database in /var/lib/rpm
Traceback (most recent call last):
  File "/usr/bin/yum", line 29, in <module>
    yummain.user_main(sys.argv[1:], exit_code=True)
  File "/usr/share/yum-cli/yummain.py", line 301, in user_main
    errcode = main(args)
  File "/usr/share/yum-cli/yummain.py", line 155, in main
    base.getOptionsConfig(args)
  File "/usr/share/yum-cli/cli.py", line 188, in getOptionsConfig
    self.conf
  File "/usr/lib/python2.6/site-packages/yum/__init__.py", line 630, in <lambda>
    conf = property(fget=lambda self: self._getConfig(),
  File "/usr/lib/python2.6/site-packages/yum/__init__.py", line 227, in _getConfig
    self._conf = config.readMainConfig(startupconf)
  File "/usr/lib/python2.6/site-packages/yum/config.py", line 772, in readMainConfig
    yumvars['releasever'] = _getsysver(startupconf.installroot, startupconf.distroverpkg)
  File "/usr/lib/python2.6/site-packages/yum/config.py", line 842, in _getsysver
    idx = ts.dbMatch('provides', distroverpkg)
TypeError: rpmdb open failed

Additional information:
rpm -q still works

rpm-4.6.0-2.fc11.i386
rpm-python-4.6.0-2.fc11.i386
glibc-2.9.90-3.i686
Linux 2.6.29-0.96.rc3.git12.fc11.i586