"DSO-Exploit is a security gap in Internet Explorer, Outlook and Outlook Express. Microsoft did already close this gap with security updates, so with current Windows updates and patches installed, it will no longer be a threat to your system.
Spybot-S&D will still detect the DSO-Exploit, but instead of fixing it for good, it will unfortunately again set an invalid value. Therefore it will again be found with every scan.
This little bug in Spybot-S&D has already been repaired and the respective fix will soon be available as a program update."
- taken from Spybot's website.