Outlook 2010 is broken and that's nothing new. What was new for me was Outlook 2010 not displaying list bullets, but every other email client did show them correctly.
The solution to this problem is simple, once discovered: Remove all styles attached to those lists and Outlook 2010 will display standard list bullets correctly. In this case the styles were an extra margin and padding, added to the
<ul> element. I didn't have the time to investigate further yet, but for sure would it be interesting, if this only happens with certain styles or with any.