I just did a quick check on my computer. Your sample code runs perfectly fine on my machine, regardless if you comment or uncomment the level_load statement. So basically I see four possible error sources:
- Your .wmb file is damaged. Recompiling should solve the issue then.
- Your source image is somehow different or damaged. I made a 24 bit .tga file.
- Your hardware or any of your drivers is causing the problem.
- You posted only an excerpt of your code and something totally different is causing the problem.