I have not tried the sample applications, but crashes like that sounds like there is something that goes wrong in the native side of the application (in streamengine.dll) rather than the managed side, but it could of course be triggered by a bad call to the interop methods. If it differs between debug and release, it could indicate that there is a timing-factor, or that the GC behaves differently in debug and release for example.
Do you do any lengthy operations in the gaze callback? You should typically avoid doing any thing that requires dispatching to the UI thread or anything that takes longer than a few milliseconds to avoid blocking the sending thread for too long.