Error Message:
If you are getting an error message stating that resource file is missing, it’s because the language resource files were not copied to the global resources folder of the Web App after solution deployment. It should have been copied if the WSS Timer Service has the appropriate permissions to successfully execute custom job that is scheduled when product feature was installed – where it copies resource files.
How To Fix:
To fix it, just run CopyAppBinContent command from stsadm on each WFE, and you will have the language resource files available for the web applications to use.