Do you have multiple threads in your application? If you do so it is possible that you (or the derelict library) does a API call in a different then the main thread which might lead to the error you describe. As the GC runs the destructors in any arbitrary thread you can not free any SDL resources inside a destructor.
No, I have no other threads. But currently I'm working on my VBO, so it could take some time until I could search for the problem and a possible solution.
