This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Try adding the List elements to some duplicate free, order-preserving collection (a SortedSet, eg a LinkedHashSet), clear the List, and refill it from the set. Then, you have the elements in the List in the same order as before, but without the duplicates.