The source of your problem lies in one of three areas
1. The registry entry used by the automation library to determine where the T4 templates is missing
2. The template does not store which version of the template to use
3. The file and or templates directory does not exist
So here is what you need to do look for hte following registry key
on 32bit OS
On 64bit os
Look for the value TemplatePath
Confirm that the directory and the template file exists.
If it does not then you will need to repair the install and to pull down the tt templats and recreate the directory, or to recreate the registry entry.
If those do exist then please let me know