It came to our attention that some users were experiencing problems with WP Include File v.22.214.171.124 and WordPress 3.0 and above. We were unable to reproduce any problems on our test servers, hence we concluded that the problems were due to incorrect setup of the file paths.
Therefore, WP Include File v.126.96.36.199 works just fine with WordPress 3.0 and WordPress 3.0.1.
However, we have released today WP Include File v.188.8.131.52. This version introduces the Debug Mode to address the problems with incorrect set up of the included file paths. Once enabled, if the file is not found, WP Include File will yield a message in the post page stating where (the path) it is looking for the included file. This will help avoid confusion and save time in setting up the plugin.
You can download the latest version from WordPress Plugin Repository.
You can read more about WP Include File here.