Yep, if you burn a disc at 8x or 12x with your GH22, then try a Transfer Rate Test (Benchmark tab -> Transfer Rate Test), can you post the result?
If the GH22 has any problem reading the disc, it will show up on the graph.
I'm really not keen on my own GH22NS50, either. I used it - hooked up both internally, and externally using an adapter like Enrico's - and gave up after a couple of weeks, after putting all sorts of media through it. I now keep mine as a spare if one of my usual burners goes South