An experimental version of the tintii plugin for users of 64-bit Photoshop CS4 on Windows is now available. It may be downloaded from here. A couple of minor bug fixes have also been made to the 32-bit Windows, Mac and Linux releases, all of this coming under a new version number of 2.2.3.
The standard version of tintii will work for most users. The 64-bit version is only required if you are specifically using the 64-bit version of Photoshop CS4 on Windows. As this version is very fresh, please let me know whether or not it works for you.