I have been experimenting with the BMW test image by Mike Pan and here are my results.
OS - Windows 64 bit Pro
CPU - AMD Phenom II x6 1055T
GPU - ATI Radeon 5830 HD
CATALYST - 12.4 beta
RAM - 8gb
BLENDER - 2.62.3 r45555 (alb3530 GraphicAll.org)
The first time after installing the 12.4 catalyst took 4 minutes to compile kernels - a 4 minute pause before rendering - and then a render time of 1:16.13 with the following result:
I tried several different images, all with the same color issue in the render so I decided to try some things.
This is a render with the background image removed (under the world tab) with a render time of 1:10.76 :
If you remove the image texture for the windows they show up but with a lot of noise for 200 passes. I found that with any image I tested I had to remove the image texture for it to work and just use color.
I also found that as long as you worked on the same image the render was fast but if you changed to a new image it would always have a 4 minute pause after the BVH build before the render starts. Is this a compiling pause or is it another issue?