Re: How can GDAL driver support 16(32)-bit color images?
I faced this problem before as you can see in this post.
And the solution is to made some modification to the gdal driver that you can find them in the following two files. These changes will allow you to load any image, and also to change the bands to render (but still cannot remove the image cache).
These changes are not perfect, so you can work arround them if you face any problem.