Are you using the binary version of DevIL? You could try to compile the source code, link it to your project and debug it, so you can see what is happening. Or, simpler, you could just get the error code out of DevIL and see what does it mean. DevIL will store error codes for you, so immediately after your code encounters an issue, try finding out what error code you get.
At the moment, I use the SOIL-Library. I tried it also with DevIL but then I had the problem, that all of the textures are completely black.