Many thanks for your response. I am using the latest version of FF (3.0.8.) and the latest version of Adobe Flash Player (10.0.22.87). In FF 3.0.8 the front page looks like this:
In IE, Opera, and older versions of FF the front page looks like this:
If it was for the front page only, I could simply re-size the images to the display size and be done with it, but I have about 60 galleries on fmueller.com, and more on other sites I am running. Maybe I am making more out of this problem then it is, since it affects only users of the latest version of FF, and even there the gallery view is still ok. However, the slideshow view is horrible in FF 3.0.8, and I have always aimed for the site to look best in FF. Even if you can't help, can you suggest anything I could do or anybody I could contact?
Also, I always thought the parameter 'stretch image' under gallery/options/slideshow should control if the image is downsized to fit the slideshow in slideshow view. However, if I set this parameter to true, false, fit, or none makes no difference to the appearance of my slideshows in either browser. Do you have any idea why that is? Maybe there is something wrong with my site after all?