Thanks for the information, design_dolphin.
I only have a small, basic webpage (about 12 html files with text and pictures) with no fancy stuff like flash animations and things like that. There is also very little traffic on my site.
I followed the instructions on codex.www.ads-software.com carefully and tried a manual install in a separate directory on my web site; I changed the name of the wordpress folder (originally “wordpress”) accordingly. The error message seems to indicate a memory problem, but it sounds strange …