I have an idea... but it will be a pain the rear...
1. Open up VSB, import Vista theme
2. Edit button works as it bypasses the open/save dialog window (anything using the dialog window doesn't work for some reason).
3. After done editing image, save image, or save image to a folder and drag & drop to the VSB image preview, effectively importing the image and bypassing the dialog window
4. Test theme, if theme testing works, then VSB should actually compile (save) the theme as a temp file in %temp% in the form of ave****.tmp.
5. Go to %temp% and change view to DateModified. Search for the latest ave****.tmp file. Rename it to your theme name.msstyles and drag it over to your theme folder and restart the process.
Yeah, that's a bit too much work. Oh well.
Hopefully we'll get an update soon