i mess it up when Enabling Flash Plugin in firefox.

[enhu]

[root@enhu Download]# su -c 'yum install flash-plugin nspluginwrapper.x86_64 \
>     nspluginwrapper.i586 alsa-plugins-pulseaudio.i586 \
>     libcurl.i586'
Loaded plugins: refresh-packagekit

Existing lock /var/run/yum.pid: another copy is running as pid 3703.
Another app is currently holding the yum lock; waiting for it to exit...
  The other application is: yum
    Memory :  43 M RSS ( 55 MB VSZ)
    Started: Sat Oct  3 00:36:31 2009 - 13:48 ago
    State  : Traced/Stopped, pid: 3703
Another app is currently holding the yum lock; waiting for it to exit...
  The other application is: yum
    Memory :  43 M RSS ( 55 MB VSZ)
    Started: Sat Oct  3 00:36:31 2009 - 13:50 ago
    State  : Traced/Stopped, pid: 3703

this keeps going on and on and it don't end until i hit ctrl c.
what does this error mean and how can i solve this?

[daark.child]

Its seems like there is another app using yum (maybe the package updater). Try the following

service yum-updatesd stop

After that try installing the packages you need.