Another dumb error message.
While installing ActiveWriter, it asked me to install DslToolsRedist. Trying to do so raised the said error message. I was on my way to shot the admin, but then googled a bit, and found out on http://www.appdeploy.com/messageboards/tm.asp?m=8872&mpage=1 that it is caused by prior installations of he same product that was not fully removed from the registry while uninstalled. Searching "DSL" in HKEY_CLASSES_ROOT\Installer\Products\ showed me that a previous CTP left some dirt in my registry. Removed that key, reinstalled DslTools and the ActiveWriter magic could finally started.