If you have any issues with distribution of any packages to child sites or if you are in multi-tier hierarchy,You get face issues with packages not replicating to child sites due to several reasons and they will be retrying n (specific) number of times until they get right version of PCK file.
Preload is Our Friend to fix Package replication issues in better way. To know more about Preload Tool and its usage http://blogs.technet.com/b/configurationmgr/archive/2009/05/07/configmgr-2007-the-preload-package-tool-preloadpkgonsite-exe-explained.aspx
How do you copy the PCK files ? Via Network Share ? sending them Via disk if you have large number of packages (this may happen when building new site) or different method ?
I use Robocopy oftenly if there are any Big Packages(more than 1GB or even less you can use) to copy even if there are any network breakage/Restart, it keeps retry.
Here is the syntax used to copy the PCK file.
robocopy sourcename Destination [Filename /Z
Ex: robocopy \\CM07\f$\smspkg G:\smspkg\ Cen00C01.pck /z
/Z : copy files in restartable mode
To know more about Robocopy ,use Robocopy /?
Download Robocopy from here