When running yum upgrade I got this:

Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/yum/rpmtrans.py", line 389, in callback
    self._scriptError(bytes, total, h)
  File "/usr/lib/python2.6/site-packages/yum/rpmtrans.py", line 510, in _scriptError
    remove_hdr = False # if we're in a clean up/remove then hdr will not be an rpm.hdr
  File "/usr/lib/python2.6/site-packages/yum/rpmtrans.py", line 237, in _dopkgtup
    tmpepoch = hdr['epoch']
TypeError: string indices must be integers, not str
error: python callback <bound method RPMTransaction.callback of <yum.rpmtrans.RPMTransaction instance at 0x7fde4c7ebf80>> failed, aborting!
[root@hubmaier ~]# 

Version-Release number of selected component (if applicable):
yum-3.2.21-16.fc11.noarch (or maybe -12 -- I have duplicate packages)

How reproducible:
happened once 

Steps to Reproduce:
1.yum upgrade
2.
3.
  
Actual results:
see above

Expected results:
nicely upgraded system and no messages

Additional info: