If it can be of any help – it looks like it was the ‘Social Discussions’ plugin by LinksAlpha to create the problems with the Suffusion dashboard.
Hey! That did work, thank you – now the tabs and floating window in the Suffusion options are back to normal behaviour, and changes are saved all right. I had to DELETE all my dear plugins, though ;), as you said, disabling was not sufficient. Still it does not help for the thumbnail issue on the magazine template.
I use Firefox 3.6.13.
