Yum: No Packages marked for Update/Obsoletion -- when there obviously are!

[tokyoi at mac.com]

I am having a puzzling problem with yum. I have not updated my FC6 box 
(Pentium 4) since December but '$sudo yum update' told me that there 
were no packages marked for update. Puzzled, I gave myself root 
privileges using 'su -' and did a clean-up using the command,

# yum clean all

This started to look promising, but the same message was returned after 
it had chewed through the repos:

[root at tokyoii ~]# yum update
Loading "installonlyn" plugin
Setting up Update Process
Setting up repositories
livna                     100% |=========================| 2.1 kB    00:00
adobe-linux-i386          100% |=========================|  951 B    00:00
core                      100% |=========================| 1.1 kB    00:00
updates                   100% |=========================| 1.2 kB    00:00
extras                    100% |=========================| 1.1 kB    00:00
Reading repository metadata in from local files
primary.xml.gz            100% |=========================|  66 kB    00:00
livna     : ################################################## 222/222
primary.xml.gz            100% |=========================| 1.3 kB    00:00
adobe-linu: ################################################## 2/2
primary.xml.gz            100% |=========================| 824 kB    00:01
core      : ################################################## 2242/2242
primary.xml.gz            100% |=========================| 475 kB    00:01
updates   : ################################################## 1285/1285
primary.xml.gz            100% |=========================| 1.7 MB    00:03
extras    : ################################################## 5211/5211
No Packages marked for Update/Obsoletion
[root at tokyoii ~]#  

On the off-chance, I also restarted the updates daemon, even though as I 
understand it this would not have any effect on the actual updating 
process, but this has not changed anything either. I have not changed my 
yum config files since installation (except to keep a few more copies of 
packages than the standard 2 (as per installonlyn.conf). Yesterday I 
installed qtparted with yum just to see if that would work and it did. I 
have looked through the man pages and done some googling but nothing on 
precisely this problem, as far as I can see. I should add that I have 
seen this before but it has "just" cleared up.

Any ideas?

Many thanks in advance,

Ian Astley