Well, this was quick! I cracked it:
@Html.ActionLink(titleText,
Title.Href.TargetAction,
Title.Href.TargetController,
Title.Href.TargetRouteValues,
new Dictionary<string, object> { { "target", "_blank" } })
This got me out. Instead of providing an anonymous object for the HTMLAttributes, i used an IDictionary, and it now works like a charm.
Thanks for the interest, however, Nick, your solution is not valid ;)