it seems that the Gallery module (v 0.2.2) and Silverstripe 2.3.0 causes some problems in combination with the static publisher extension.
What happened was that the page was saved but the site tree in the CMS on the left was not updated. I had to refresh the page to get an up-to-date site tree.
Do I have to enable the static publisher for individual modules or can anyone think of other reasons why this happens? I enabled the static publisher in /mysite/code/Page.php and /mysite/_config.php and I assumed that it would then work for any page including modules.