Description of problem:
On new installation of Fedora 11 (see below URL at bottom of this description for details/further examples, but 32 and 64-bit editions seem to be affected according to below URL), a 'yum update' fails on several packages (SEE ADDITIONAL INFO BELOW).

Those packages either excluded via --exclude=[package-name] or in /etc/yum.conf finally cause a yum update to function.  

Without the exclusion of later mentioned packages, the following errors occur:
Downloading Packages:
http://linux.nssl.noaa.gov/fedora/linux/updates/11/i386/gnome-common-2.26.0-2.fc11.noarch.rpm: [Errno 14] HTTP Error 404: Not Found
Trying other mirror.
ftp://fedora.bu.edu/updates/11/i386/gnome-common-2.26.0-2.fc11.noarch.rpm: [Errno 4] IOError: [Errno ftp error] 450 gnome-common-2.26.0-2.fc11.noarch.rpm: No such file or directory
Trying other mirror.
 (and so forth)
 #### OUTPUT TRUNCATED FOR BREVITY #####

Attempting the next 2 commands provided no relief to this issue (see URL at end). 
root@mysystem # yum clean all
or
root@mysystem # yum clean metatdata

Removing the mirror lines in the /etc/yum.repos.d/fedora.repo and uncommenting the 'baseurl' provided no relief either (and subsequent 'yum clean all' prior of course).
[root@mysystem yum.repos.d]# cat /etc/yum.repos.d/fedora.repo 
[fedora]
name=Fedora $releasever - $basearch
failovermethod=priority
baseurl=http://download.fedoraproject.org/pub/fedora/linux/releases/$releasever/Everything/$basearch/os/
#mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=fedora-$releasever&arch=$basearch
enabled=1
metadata_expire=7d
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-$basearch
### OUTPUT TRUNCATED FOR BREVITY ###

Subsequent 'yum update' failed ad-nauseum:

http://download.fedoraproject.org/pub/fedora/linux/releases/11/Everything/i386/os/repodata/35d817e2bac701525fa72cec57387a2e3457bf32642adeee1e345cc180044c86-primary.sqlite.bz2: [Errno 4] Socket Error: timed out
Trying other mirror.
http://download.fedoraproject.org/pub/fedora/linux/releases/11/Everything/i386/os/repodata/35d817e2bac701525fa72cec57387a2e3457bf32642adeee1e345cc180044c86-primary.sqlite.bz2: [Errno 12] Timeout: <urlopen error timed out>
Trying other mirror.


Version-Release number of selected component (if applicable):
root@mysystem # rpm -qi `rpm -qa | grep yum`

A backend for PackageKit to enable yum functionality.
Name        : yum                          Relocations: (not relocatable)
Version     : 3.2.23                            Vendor: Fedora Project
Release     : 3.fc11                        Build Date: Wed 20 May 2009 06:29:32 PM EDT
Install Date: Tue 16 Jun 2009 10:30:21 PM EDT      Build Host: x86-4.fedora.phx.redhat.com
Group       : System Environment/Base       Source RPM: yum-3.2.23-3.fc11.src.rpm
Size        : 3541271                          License: GPLv2+
Signature   : RSA/8, Sat 23 May 2009 12:15:49 PM EDT, Key ID 1dc5c758d22e77f2
Packager    : Fedora Project
URL         : http://yum.baseurl.org/
Summary     : RPM installer/updater


How reproducible:
Very often, various persons reported this at FedoraForums, URL at bottom of this description.

It seems from the context of the people at FedoraForum that their repositories are not polluted with incompatible repositories.

There's six pages of various persons having this specific problem revolving around these packages.

One of the users at the URL at bottom reported this occurred even after a fresh/clean install of Fedora 11 (today, 7/12/2009).  

Steps to Reproduce:
1.  Go to a Fedora 11 system,  
2.  Perform the command 'yum update' (without any exclusions in command line or in /etc/yum.conf ) 
3.  Accept the proposed yum download/update.  (See further examples in the URL at bottom of this description). 
  
Actual results:
Excluding the packages listed in "Additional info" below caused a yum update to work.  One other user in the URL below (Steve) did not need to exclude 'gnome-common' in his specific case.

Expected results:
Typical expectations for a 
root@somesystem # yum update
are that it will work without errors described above.

Additional info:
As a (very) temporary "work-around" (ugh), the following was executed with limited success (see URL below)
root@mysystem #   yum \
--exclude=alsa-plugins-pulseaudio \
--exclude=dhclient \
--exclude=farsight2 \
--exclude=gdb \
--exclude=grubby \
--exclude=gstreamer-plugins-good \
--exclude=gnome-common \
--skip-broken \
update

Nearly documented at:
http://forums.fedoraforum.org/showthread.php?p=1240858&posted=1#post1240858