I had the same problem. Here’s how I brought with me to run the slideshow:
– Follow the instruction of gnocchi. Very important that the path in slideshow options include the filename of the stored imagerotators.swf: http://www.yourdomain.ch/wp-content/uploads/imagerotator.swf
Additionally, I have moved the imagerotator.swf file into the plugins directory to the folder of Nextgen Gallery (like the instructions of tomasi514). Whether it’s helped, I can not say right. Now that I’ve deleted the file from this plugin folder, the slideshow works still.
But perhaps this step is necessary.
