Hi Klaus,
Have a look at this screen shot: http://img88.imageshack.us/img88/6071/ssblackcanvasbl2.jpg
This is a cylinder pano and when I rotate it, extra black space (1 to 2 pixels) shows up at the top. This is using 1.0.8 Beta 4. This doesn't show up in 1.0.8 Beta 1 so not sure what code you changed or encountered some bugs along the way?
Please let me know if you can fix this ? Thank you !