Since the release of Joomla 2.5 there has been a particularly annoying “duplicate template” bug that becomes clearly evident when you install or update a template. This has caused a great deal of confusion and consternation among Joomla users, but nobody offered an easy to use fix until recently. As anyone else in this business I hit the wall with this bug, until I found a cure for it on RocketTheme's blog.
The bug was identified and patched in the Joomla platform shortly after the 2.5.0 release, however, Joomla is currently at 2.5.4 at the time of this writing and this issue remains because the Joomla platform fix has not been merged into the Joomla CMS code. Even when this fix makes it into the Joomla CMS codebase, it will not fix the multiple duplicate database entries that result from the buggy template installer file.
In an effort to address this, RocketTheme created a simple Joomla plug-in that patches the core template installer file with the relevant fix from the updated Joomla platform code as well as removing the erroneous extra database entries. On installation, the plug-in does it’s work, and won’t attempt to fix anything again until you toggle the “Patch Every Page-Load” option in the plug-in parameters. If you turn this on, the plug-in will patch and try to clean the database on every reload of the administrator. So just toggling this on, and then saving and then off again, should be good enough to refresh the process if you should need it. Also if you wish to revert the patch and go back to the original (but buggy) file, you can simply un-install the plug-in.
Read the full story, download the plugin at RocketTheme