You have errors in your template extraction code.

Chmod your template directory to 644 and try to install the plugin. You'll get an error like:

Can't locate method "error" via package PHP_PPC_Banner at Install.pm line yada yada

You need to change all occurances of:

$file->write or return PHP_PPC_Banner->error( ... );

to

$file->write or return Plugins::PHP_PPC_Banner->error( ... );

You might want to add an option in the installer to allow the user to confirm whether or not to overwrite templates otherwise it will get annoying if you customize the plugin templates and the installer overwrites them if you ever install it again..