Nero not cleaning up

I am developing an application in VB.NET with burning functionality using the Nero 1.07 SDK. I have everything working except for one problem where after calling the method NeroDrive.BurnIsoAudioCD the application will not close. I have attempted all sorts of things to clean up Nero (unsubscribing event handlers, calling ReleaseComObject etc) but nothing seems to work. I then tested the demo application in C# with the SDK and this is having the same problem?!

Any help would be appreciated.